with a chapter on Multiple Pregnancy in Scotland · forceps and vacuum extractor or ventouse) in...

18

Operative Vaginal Delivery in Scotland

A 20 year overview

with a chapter on Multiple Pregnancy in Scotland

Births in Scotland Publication Series Volume 4

SPCE

RH PUBLICATIONNUMBER

Information & Statistics DivisionNHSScotland

Scottish Programme for Clinical Effectiveness in Reproductive Health

Edinburgh 2003

Operative Vaginal Delivery in Scotland

A 20 year overview

with a chapter on Multiple Pregnancy in Scotland

© Common Services Agency/Crown Copyright 2003

Brief extracts from this publication may be reproduced provided the source is fullyacknowledged. Proposals for the reproduction of large extracts should be addressed to ISD Publications, Trinity Park House, Edinburgh EH5 3SQ.


ISBN 1-902076-17-6

Information & Statistics Division

Publication enquiries

ISD Customer Support DeskTrinity Park HouseEdinburgh EH5 3SQTel 0131-551 8899email [email protected] or


Programme Administrative Office Reproductive and Developmental Sciences Simpson Centre for Reproductive HealthRoyal Infirmary51 Little France Crescent Edinburgh EH16 4SA

Tel 0131 242 2696 Fax 0131 242 2695

email [email protected]

Typeset by ISD Scotland Publications

iii

Contents

Page

Conventions, Abbreviations and Defintions iv Acknowledgements v Operative Vaginal deliverySummary 1

Introduction 2

Time trends in mode of delivery 2

Hospital-level variation 10

Neonatal outcomes 12

Mortality 12Health service utilisation 15

Postpartum hospital stay 15Maternal morbidity 18

Third degree tear 18 Subsequent fertility 21 Urinary and anal incontinence 22Chapter References 23

Multiple Pregnancy in Scotland

Background 25

Incidence and time trends in Scotland 25

International Comparisons 28

Antecedents and associations of multiple birth 28

Maternal age 28 Parity 31 Maternal height 32 Socio-economic deprivation 34 Relative importance of associations with multiple pregnancy 35Monozygous and dizygous twinning 35

Obstetric consequences of multiple pregnancy 37

Pregnancy complications 37 Mode of delivery 40Fetal and infant consequences of multiple birth 41

Mortality 41 Preterm birth and low birthweight 45 Congenital anomalies 45 Neonatal unit service utilisation 46Chapter References 47

iv

CONVENTIONS, ABBREVIATIONS AND DEFINITIONS

The following symbols and abbreviations have been used:

.. not available - nil 0.0 negligible AP Antepartum APH Antepartum haemorrhage GRO(S) General Register Office (Scotland) IP Intrapartum IUD Intrauterine death SIDS Sudden infant death syndrome SB Stillbirth NND Neonatal death ENN Early neonatal death LNN Late neonatal death PNND Postneonatal death

SVD Spontaneous vertex delivery ELCS Elective caesarean section EMCS Emergency caesarean section OVD Operative vaginal delivery CS Caesarean section

National Statistics Definition

Unless otherwise specified in the “Data Sources” section, the figures contained in this publication are ‘National Statistics’. National Statistics are produced to high professional standards, and adhere to commitments relating to integrity, confidentiality, burden of collection, liaison and consultation, openness, access and timeliness. National Statistics undergo regular quality assurance reviews to ensure that they meet customer needs, and they are produced free from political interference. National Statistics releases are grouped under one of 13 broad subject headings (themes); this belongs to the Health and Care theme. Further details on National Statistics are contained at the National Statistics website (http://www.statistics.gov.uk/).

Stillbirths

Section 56(1) of the Registration of Births, Deaths and Marriages (Scotland) Act 1965 defined a stillbirth as a child which had issued forth from its mother after the 28th week of pregnancy and which did not breathe or show any other sign of life. The Stillbirth (Definition) Act 1992, which came into effect on 1 October 1992, amended Section 56(1) of the 1965 Act (and other relevant UK legislation), replacing the reference to the 28th week with a reference to the 24th week.

Neonatal deaths refer to deaths in the first four weeks of life. Early neonatal deaths refer to deaths in the first week of life. Late neonatal deaths refer to deaths in weeks two to four of life.

Postneonatal deaths refer to deaths after the first four weeks but before the end of the first year.

ACKNOWLEDGEMENTS

The Scottish Perinatal Mortality and Morbidity Review Advisory Group (SPMMRAG) administers the Scottish Stillbirth and Infant Death Survey on behalf of the Chief Medical Officer, and produces Annual Reports. Since 1997, SPMMRAG has also produced biennial reports in the Births in Scotland series. These reports review important perinatal and reproductive health topics using the wealth of national data routinely collected by ISD. The first three volumes of Births in Scotland were published jointly by ISD and SPCERH and distributed widely among reproductive health professionals in Scotland.

For the last two years, and in line with Scottish Executive policy, these reports have been produced only as a web-based publications. At the end of 2002, the Annual Report for 2001 and the fourth Births in Scotland volume, on Operative Vaginal Delivery in Scotland, were published within Scottish Health on the Web (SHOW). In addition to the traditional statistics, the 2001 SPIMMR included a substantial clinical chapter on Multiple Pregnancy in Scotland.

Web-based publication allows economic and timely distribution of national data to a wide group of professionals and the public. However, large numbers of reproductive health professionals, particularly those working in community settings, do not have ready access to the internet. SPMMRAG members felt that the information contained in the Operative Vaginal Delivery report and the Multiple Pregnancy chapter could usefully be presented in a paper publication in order to reach the widest range of readers.

We are delighted to have had approval to publish this fourth volume in the Births in Scotland series. It includes the material on both topics previously published electronically within SHOW. We hope that professionals will find these overviews useful for reviewing and planning their own services, for generating research questions, and for student and postgraduate teaching.

Dr Gillian Penney(SPCERH Programme Co-ordinator)June 2003

Membership of SPMMRAG 2002/2003Ian Greer Obstetrics (Chairman)Gillian Penney SPCERH (Secretary) Ian Bashford SEHDHazel Brooke Scottish Cot Death TrustJim Chalmers ISDLinda Donaldson MidwiferyKatherine McKenzie PathologyDean Marshall General PracticeAndrew Lyon PaediatricsClaire Greig Neonatal NursingHelen Ogilvie Lay representative (SANDS)David Stone Public Health

SPCERH & ISD support teamLorraine Adamson Samantha ClarkeBev DoddsScott HealdEtta Shanks

v

1Births in Scotland

Operative Vaginal Delivery

Summary : Operative vaginal delivery

1 This report provides an overview of the use and sequelae of operative vaginal delivery (with obstetric forceps and vacuum extractor or ventouse) in contemporary practice in Scotland. It is based on data from SMR02 returns for the years 1981 to 2000, covering over a million births.

2 During the 20-year period, 10.2% of all singleton, cephalic births were forceps deliveries and 2.0%, ventouse. The overall operative vaginal delivery rate (forceps plus ventouse) has remained virtually constant over time at around 12%. This is in contrast to the Caesarean section (CS) rate which increased from 8.7% in 1981 to 17.7% in 2000. Thus the increase in the CS rate is not explained by a shift from operative vaginal delivery.

3 Although the overall operative vaginal delivery rate has remained constant, the proportional use of ventouse rather than forceps has increased steadily year on year. In 1981, the ventouse rate was 0.4% and the forceps rate,12.9%; in 2000, the ventouse and forceps rates were 5.6% and 7.2% respectively.

4 There are variations among individual maternity hospitals in the rates of different modes of delivery. For the period 1996-2000, for singleton, cephalic, first births at term, hospital-level rates ranged between:

• Emergency Caesarean sections 12.4% to 19.7% (Scotland: 15.7%) • Overall operative vaginal deliveries 10.1% to 33.8% (Scotland: 23.2%) • Forceps deliveries 4.1% to 25.5% (Scotland: 14.5%)

• Ventouse deliveries 3.2% to 16.3% (Scotland: 8.7%)

5 Groups of babies with different modes of delivery have different neonatal death rates. However, the higher rates associated with certain forms of delivery are likely to be causally related to the underlying condition which dictated the mode of delivery, rather than to the delivery itself. For singleton, term babies born during the period 1991-2000, neonatal death rates (per 1000 live births) were:

• Spontaneous vertex delivery 0.9 (95% CI, 0.8-1.0) • Vaginal breech delivery 10.1 (95% CI, 5.9-16.2) • Forceps delivery 1.6 (95% CI, 1.2-2.0) • Ventouse delivery 0.8 (95% CI, 0.4-1.3) • Elective Caesarean delivery 2.1 (95% CI, 1.7-2.7)

6 Average postpartum hospital stay has decreased steadily over the last 20 years for all women. However, there is still a differential utilisation of postpartum hospital services for women delivered in different ways. During the recent period, 1996-2000, average postpartum stay was 3.0 days for spontaneous vertex delivery; 3.5 days for forceps or ventouse deliveries and 4.8 days for Caesarean deliveries (elective or emergency).

7 Rates of third degree perineal tear vary with different modes of delivery. However, it may be the obstetric problems which prompted the use of forceps rather than ventouse which explain the higher rate of tears, rather than the use of forceps per se. For the 10-year period, 1991-2000, rates of third degree tear were:

• Spontaneous vertex delivery 5.4/1000 95% CI, 5.1-5.8 • Forceps deliveries 16.1/1000 95% CI, 14.8-17.4 • Ventouse deliveries 9.9/1000 95% CI, 8.3-11.6 • Vaginal breech deliveries 1.8/1000 95% CI, 0.0-10.2

8 Linkage between the different datasets held by ISD will enable us to examine rates of the long-term sequelae of different modes of delivery (eg urinary and anal incontinence). Additional analysis may also help explain hospital level variations.

2 Births in Scotland


3Births in Scotland


Introduction

The Births in Scotland biennial publication series, a joint initiative between ISD and the Scottish Programme for Clinical Effectiveness in Reproductive Health (SPCERH), began in 1997. The aim of the series is to present data routinely collected by ISD through SMR02 and related datasets in the context of clinically important topics. The 1997 volume, Births in Scotland 1976-1995, 1 marked 20 years of continuous maternity data collection through SMR02 and provided an overview of changes in reproductive health over that time period. Subsequent volumes focused on preterm birth and low birthweight2 and on babies with congenital anomalies.3

This fourth volume is devoted to issues around operative vaginal delivery. In recent years, there has been much debate and study of the role of Caesarean section in contemporary maternity care and previous SPCERH publications have addressed the rising Caesarean section rate.4,5 The Scottish Perinatal Mortality and Morbidity Review Advisory Group (SPMMRAG) oversees the production of these BIS Reports. This Group felt that the problems and benefits of operative vaginal delivery had been somewhat neglected in the general debate - and that this represents a worthwhile topic for study using Scotland’s routine data.

In this volume, we summarise data on time trends and unit-level variation in mode of delivery, and on infant and maternal sequelae. The data presented are derived from 20 years of SMR02 returns (1981 to 2000), covering over a million births in Scotland. The information that SPMMRAG wished to present relating to maternal and infant sequelae involves data linkage between the various datasets held by ISD.

Time trends in mode of delivery

The following data are based on SMR02 returns for singleton, cephalic births during the 20 year period, 1981 to 2000 (1,155,590 births). Overall, 76% of these babies were born by spontaneous vaginal delivery (with the percentage falling steadily from 78% in 1981 to 69% in 2000). Ten percent were born by forceps delivery, with this percentage falling steadily from 13% in 1981 to seven percent in 2000. Overall, only two percent of babies were delivered using the ventouse, though this percentage increased over time from 0.4% in 1981 to almost six percent in 2000. The remaining babies (12% overall) were delivered by Caesarean section; again with a steady increase over the 20 years, from nine to 18%.

Figure1 and Table1 summarise data on mode of delivery for singleton, cephalic births. Overall operative vaginal delivery rates (forceps plus ventouse) have remained remarkably constant, at around 12%, over the 20-year period. The rise in Caesarean section over the 20-year period is reflected by a fall in spontaneous deliveries, rather than by any fall in operative vaginal births.

Figure 1 - Singleton, cephalic presentations, by mode of delivery (1981-2000)

0

10

20

30

40

50

60

70

80

90

csections

operative

svd

20001999199819971996199519941993199219911990198919881987198619851984198319821981

Percentage



3Births in Scotland


Mode of deliveryNumbers

svd breech1 all forceps ventouse elcs emcs not known Total

1981 48 986 14 8 116 249 1 818 3 673 18 62 8741982 47 645 8 7 568 239 1 874 3 909 16 61 2591983 47 289 1 7 132 178 1 838 3 876 7 60 3211984 47 152 0 7 360 161 2 040 3 803 17 60 5331985 47 929 7 7 015 190 2 083 4 005 3 61 2321986 47 690 4 6 836 320 2 022 4 134 4 61 0101987 47 767 4 6 253 351 1 896 4 151 47 60 4691988 47 404 1 6 985 395 1 937 4 585 21 61 3281989 45 249 4 6 689 707 1 976 4 345 47 59 0171990 46 045 3 6 735 747 1 988 4 611 17 60 1461991 47 200 1 6 632 869 2 087 4 729 11 61 5291992 45 500 1 6 328 1 053 2 204 4 825 11 59 9221993 43 856 0 5 409 1 428 2 189 4 923 31 57 8361994 42 442 2 4 865 1 872 2 146 4 688 12 56 0271995 41 714 3 4 392 2 054 2 158 4 692 8 55 0211996 39 976 10 3 962 2 215 2 153 4 856 5 53 1771997 40 234 8 4 090 2 352 2 475 5 176 6 54 3411998 37 881 10 3 907 2 623 2 466 5 699 3 52 5891999 35 376 6 3 749 2 690 2 558 5 797 7 50 1832000 32 474 9 3 355 2 614 2 547 5 771 6 46 776Total 879 809 96 117 378 23 307 42 455 92 248 297 1 155 590

Percentagessvd breech1 all forceps ventouse elcs emcs not known Total

1981 77.9 0.0 12.9 0.4 2.9 5.8 0.0 100.01982 77.8 0.0 12.4 0.4 3.1 6.4 0.0 100.01983 78.4 0.0 11.8 0.3 3.0 6.4 0.0 100.01984 77.9 - 12.2 0.3 3.4 6.3 0.0 100.01985 78.3 0.0 11.5 0.3 3.4 6.5 0.0 100.01986 78.2 0.0 11.2 0.5 3.3 6.8 0.0 100.01987 79.0 0.0 10.3 0.6 3.1 6.9 0.1 100.01988 77.3 0.0 11.4 0.6 3.2 7.5 0.0 100.01989 76.7 0.0 11.3 1.2 3.3 7.4 0.1 100.01990 76.6 0.0 11.2 1.2 3.3 7.7 0.0 100.01991 76.7 0.0 10.8 1.4 3.4 7.7 0.0 100.01992 75.9 0.0 10.6 1.8 3.7 8.1 0.0 100.01993 75.8 - 9.4 2.5 3.8 8.5 0.1 100.01994 75.8 0.0 8.7 3.3 3.8 8.4 0.0 100.01995 75.8 0.0 8.0 3.7 3.9 8.5 0.0 100.01996 75.2 0.0 7.5 4.2 4.0 9.1 0.0 100.01997 74.0 0.0 7.5 4.3 4.6 9.5 0.0 100.01998 72.0 0.0 7.4 5.0 4.7 10.8 0.0 100.01999 70.5 0.0 7.5 5.4 5.1 11.6 0.0 100.02000 69.4 0.0 7.2 5.6 5.4 12.3 0.0 100.0Total 76.1 0.0 10.2 2.0 3.7 8.0 0.0 100.0

1 Breech deliveries represent cases where the presentation was misdiagnosed or changed during labour.

Singleton cephalic presentations by year and mode of delivery, 1981-20001

Source: ISD(Scotland), SMR02



5Births in Scotland


Figure 2 summarises data on operative deliveries (again restricted to singleton cephalic births) in more detail. It clearly demonstrates that ventouse deliveries have risen while use of forceps has fallen – leaving the overall operative vaginal delivery rate fairly constant.

Table 2 shows similar summary data for singleton, cephalic births – this time restricted to first births at term (≥ 37 weeks). Operative vaginal deliveries are commoner in this group of births than in singleton, cephalic births overall. Again however, the operative vaginal delivery rate has remained fairly constant year on year (at around a quarter) with a declining use of forceps and an increasing use of ventouse.

Figure 2 - Singleton, cephalic presentations, operative deliveries (1981-2000)

0

2

4

6

8

10

12

14

operative

ventouse

all forceps

20001999199819971996199519941993199219911990198919881987198619851984198319821981

Per

cent

age

Source: ISD (Scotland), SMR 02



5Births in Scotland


2Mode of deliveryNumbers

svd breech1 all forceps ventouse elcs emcs not known Total1981 15 968 2 6 183 186 301 2 121 10 24 7711982 16 509 2 5 896 159 260 2 334 6 25 1661983 15 936 0 5 531 133 236 2 229 3 24 0681984 16 022 0 5 729 115 257 2 252 8 24 3831985 16 602 3 5 466 134 233 2 412 1 24 8511986 16 529 2 5 241 232 226 2 474 1 24 7051987 17 139 1 4 992 272 217 2 525 26 25 1721988 17 034 1 5 502 278 200 2 792 9 25 8161989 15 945 1 5 315 503 201 2 689 25 24 6791990 16 376 1 5 392 552 228 2 824 4 25 3771991 17 152 0 5 366 647 210 2 910 7 26 2921992 16 076 1 5 037 762 231 2 987 2 25 0961993 15 654 0 4 277 1 052 231 2 993 14 24 2211994 14 722 0 3 887 1 366 196 2 761 9 22 9411995 14 689 0 3 523 1 548 181 2 816 4 22 7611996 13 953 2 3 158 1 683 208 2 883 4 21 8911997 14 158 5 3 285 1 745 269 3 035 3 22 5001998 13 311 5 3 075 1 930 236 3 470 0 22 0271999 12 702 3 2 961 2 023 280 3 540 4 21 5132000 11 340 3 2 690 1 937 295 3 494 1 19 760Total 307 817 32 92 506 17 257 4 696 55 541 141 477 990


1982 65.6 0.0 23.4 0.6 1.0 9.3 0.0 100.01983 66.2 - 23.0 0.6 1.0 9.3 0.0 100.01984 65.7 - 23.5 0.5 1.1 9.2 0.0 100.01985 66.8 0.0 22.0 0.5 0.9 9.7 0.0 100.01986 66.9 0.0 21.2 0.9 0.9 10.0 0.0 100.01987 68.1 0.0 19.8 1.1 0.9 10.0 0.1 100.01988 66.0 0.0 21.3 1.1 0.8 10.8 0.0 100.01989 64.6 0.0 21.5 2.0 0.8 10.9 0.1 100.01990 64.5 0.0 21.2 2.2 0.9 11.1 0.0 100.01991 65.2 - 20.4 2.5 0.8 11.1 0.0 100.01992 64.1 0.0 20.1 3.0 0.9 11.9 0.0 100.01993 64.6 - 17.7 4.3 1.0 12.4 0.1 100.01994 64.2 - 16.9 6.0 0.9 12.0 0.0 100.01995 64.5 - 15.5 6.8 0.8 12.4 0.0 100.01996 63.7 0.0 14.4 7.7 1.0 13.2 0.0 100.01997 62.9 0.0 14.6 7.8 1.2 13.5 0.0 100.01998 60.4 0.0 14.0 8.8 1.1 15.8 - 100.01999 59.0 0.0 13.8 9.4 1.3 16.5 0.0 100.02000 57.4 0.0 13.6 9.8 1.5 17.7 0.0 100.0Total 64.4 0.0 19.4 3.6 1.0 11.6 0.0 100.0

Source: ISD (Scotland), SMR02

Singleton, first birth, cephalic presentations at term by year and mode of delivery, 1981-2000

1 Breech deliveries represent cases where the presentation was misdiagnosed or changed during labour



7Births in Scotland


3

Tables 3,4 and 5 summarise the 20-year trend in modes of delivery for singleton, first births in different gestation bands. (All these Tables refer to deliveries where the fetal presentation was recorded as cephalic at the onset of labour. In each Table, a few vaginal breech deliveries are included. These represent cases where an error was made in the recorded fetal presentation, or where the fetus turned from cephalic to breech during labour.) Figure 3 is based on the aggregate 20-year data and summarises the proportions of singleton, cephalic fetuses in different gestation bands which delivered by each of the various modes.


svd breech1 all forceps ventouse elcs emcs not known Total1981 818 1 339 3 115 139 1 1 4161982 882 2 284 1 109 180 0 1 4581983 915 0 265 3 108 188 1 1 4801984 963 0 263 0 123 210 1 1 5601985 990 2 245 3 124 213 0 1 5771986 1 012 1 226 5 123 226 1 1 5941987 965 0 189 5 70 244 6 1 4791988 1 055 0 209 8 99 281 2 1 6541989 976 0 192 13 99 284 1 1 5651990 1 009 1 214 21 79 273 2 1 5991991 1 032 0 199 13 80 338 0 1 6621992 1 047 0 209 17 85 323 0 1 6811993 970 0 165 28 75 311 3 1 5521994 928 2 134 34 76 326 0 1 5001995 918 0 129 38 63 344 1 1 4931996 886 0 114 34 66 346 0 1 4461997 873 0 93 39 76 334 0 1 4151998 856 1 122 51 57 383 0 1 4701999 786 1 126 52 57 400 0 1 4222000 792 1 118 56 56 347 0 1 370Total 18 673 12 3 835 424 1 740 5 690 19 30 393


1981 57.8 0.1 23.9 0.2 8.1 9.8 0.1 100.01982 60.5 0.1 19.5 0.1 7.5 12.3 - 100.01983 61.8 - 17.9 0.2 7.3 12.7 0.1 100.01984 61.7 - 16.9 - 7.9 13.5 0.1 100.01985 62.8 0.1 15.5 0.2 7.9 13.5 - 100.01986 63.5 0.1 14.2 0.3 7.7 14.2 0.1 100.01987 65.2 - 12.8 0.3 4.7 16.5 0.4 100.01988 63.8 - 12.6 0.5 6.0 17.0 0.1 100.01989 62.4 - 12.3 0.8 6.3 18.1 0.1 100.01990 63.1 0.1 13.4 1.3 4.9 17.1 0.1 100.01991 62.1 - 12.0 0.8 4.8 20.3 - 100.01992 62.3 - 12.4 1.0 5.1 19.2 - 100.01993 62.5 - 10.6 1.8 4.8 20.0 0.2 100.01994 61.9 0.1 8.9 2.3 5.1 21.7 - 100.01995 61.5 - 8.6 2.5 4.2 23.0 0.1 100.01996 61.3 - 7.9 2.4 4.6 23.9 - 100.01997 61.7 - 6.6 2.8 5.4 23.6 - 100.01998 58.2 0.1 8.3 3.5 3.9 26.1 - 100.01999 55.3 0.1 8.9 3.7 4.0 28.1 - 100.02000 57.8 0.1 8.6 4.1 4.1 25.3 - 100.0Total 61.4 0.0 12.6 1.4 5.7 18.7 0.1 100.0

Singleton, first birth, cephalic presentations <37 weeks by year and mode of delivery, 1981-2000

Source: ISD (Scotland), SMR021 Breech deliveries represent cases where the presentation was misdiagnosed or changed during labour



7Births in Scotland


4Mode of deliveryNumbers

svd breech1 all forceps ventouse elcs emcs not known Total

1981 149 1 52 1 15 23 0 2411982 133 1 27 0 14 38 0 2131983 136 0 31 0 23 42 0 2321984 137 0 21 0 24 45 1 2281985 144 2 26 0 24 34 0 2301986 151 1 19 0 20 45 1 2371987 127 0 13 0 10 47 1 1981988 173 0 17 0 12 60 0 2621989 133 0 11 1 14 58 1 2181990 144 1 9 1 16 57 2 2301991 168 0 15 0 14 79 0 2761992 159 0 7 0 20 83 0 2691993 150 0 9 2 23 54 1 2391994 157 1 8 0 14 92 0 2721995 137 0 13 1 12 72 1 2361996 141 0 7 0 6 80 0 2341997 112 0 2 1 13 73 0 2011998 135 1 8 0 11 80 0 2351999 115 1 12 2 7 77 0 2142000 115 1 5 0 9 82 0 212Total 2 816 10 312 9 301 1 221 8 4 677


1981 61.8 0.4 21.6 0.4 6.2 9.5 - 100.01982 62.4 0.5 12.7 - 6.6 17.8 - 100.01983 58.6 - 13.4 - 9.9 18.1 - 100.01984 60.1 - 9.2 - 10.5 19.7 0.4 100.01985 62.6 0.9 11.3 - 10.4 14.8 - 100.01986 63.7 0.4 8.0 - 8.4 19.0 0.4 100.01987 64.1 - 6.6 - 5.1 23.7 0.5 100.01988 66.0 - 6.5 - 4.6 22.9 - 100.01989 61.0 - 5.0 0.5 6.4 26.6 0.5 100.01990 62.6 0.4 3.9 0.4 7.0 24.8 0.9 100.01991 60.9 - 5.4 - 5.1 28.6 - 100.01992 59.1 - 2.6 - 7.4 30.9 - 100.01993 62.8 - 3.8 0.8 9.6 22.6 0.4 100.01994 57.7 0.4 2.9 - 5.1 33.8 - 100.01995 58.1 - 5.5 0.4 5.1 30.5 0.4 100.01996 60.3 - 3.0 - 2.6 34.2 - 100.01997 55.7 - 1.0 0.5 6.5 36.3 - 100.01998 57.4 0.4 3.4 - 4.7 34.0 - 100.01999 53.7 0.5 5.6 0.9 3.3 36.0 - 100.02000 54.2 0.5 2.4 - 4.2 38.7 - 100.0Total 60.2 0.2 6.7 0.2 6.4 26.1 0.2 100.0





9Births in Scotland




svd breech1 all forceps ventouse elcs emcs not known Total1981 149 1 52 1 15 23 0 2411982 133 1 27 0 14 38 0 2131983 136 0 31 0 23 42 0 2321984 137 0 21 0 24 45 1 2281985 144 2 26 0 24 34 0 2301986 151 1 19 0 20 45 1 2371987 127 0 13 0 10 47 1 1981988 173 0 17 0 12 60 0 2621989 133 0 11 1 14 58 1 2181990 144 1 9 1 16 57 2 2301991 168 0 15 0 14 79 0 2761992 159 0 7 0 20 83 0 2691993 150 0 9 2 23 54 1 2391994 157 1 8 0 14 92 0 2721995 137 0 13 1 12 72 1 2361996 141 0 7 0 6 80 0 2341997 112 0 2 1 13 73 0 2011998 135 1 8 0 11 80 0 2351999 115 1 12 2 7 77 0 2142000 115 1 5 0 9 82 0 212Total 2 816 10 312 9 301 1 221 8 4 677


1981 61.8 0.4 21.6 0.4 6.2 9.5 - 100.01982 62.4 0.5 12.7 - 6.6 17.8 - 100.01983 58.6 - 13.4 - 9.9 18.1 - 100.01984 60.1 - 9.2 - 10.5 19.7 0.4 100.01985 62.6 0.9 11.3 - 10.4 14.8 - 100.01986 63.7 0.4 8.0 - 8.4 19.0 0.4 100.01987 64.1 - 6.6 - 5.1 23.7 0.5 100.01988 66.0 - 6.5 - 4.6 22.9 - 100.01989 61.0 - 5.0 0.5 6.4 26.6 0.5 100.01990 62.6 0.4 3.9 0.4 7.0 24.8 0.9 100.01991 60.9 - 5.4 - 5.1 28.6 - 100.01992 59.1 - 2.6 - 7.4 30.9 - 100.01993 62.8 - 3.8 0.8 9.6 22.6 0.4 100.01994 57.7 0.4 2.9 - 5.1 33.8 - 100.01995 58.1 - 5.5 0.4 5.1 30.5 0.4 100.01996 60.3 - 3.0 - 2.6 34.2 - 100.01997 55.7 - 1.0 0.5 6.5 36.3 - 100.01998 57.4 0.4 3.4 - 4.7 34.0 - 100.01999 53.7 0.5 5.6 0.9 3.3 36.0 - 100.02000 54.2 0.5 2.4 - 4.2 38.7 - 100.0Total 60.2 0.2 6.7 0.2 6.4 26.1 0.2 100.0

5




9Births in Scotland


Figure 3 shows that term first births have a higher spontaneous vaginal delivery rate (64.4%) than preterm (<37 weeks)(61.4%) or very preterm (<32 weeks)(60.2%) first births. In contrast however, extremely preterm first births (<28 weeks) have a high rate of spontaneous vaginal delivery (78%). Various factors may explain this rate. These include precipitate births in these small infants, a reluctance on the part of clinicians to undertake operative delivery for tiny infants with a poor prognosis, and reduced risk of delay in the second stage on account of small fetal size. Operative vaginal deliveries (forceps or ventouse) are seldom undertaken for these tiniest babies; however, the emergency Caesarean section rate is higher than for term babies. The emergency CS rate for extremely preterm births does not show the clear upward trend year on year which is seen for the preterm and very preterm gestation bands.

Figure 3 - Singleton cephalic presentations by mode of delivery, 1981-2000 (aggregated)Source: ISD (Scotland), SMR2/SMR02

svd breech all forceps ventouse elective CS emergency CS

Total1

All singletons 76.1 0.0 10.2 2.0 3.7 8.0 100.0

First births at term 64.4 0.0 19.4 3.6 1.0 11.6 100.0

First births <37 weeks 61.4 0.0 12.6 1.4 5.7 18.7 99.9



0

20

40

60

80

100emergency CS

elective CS

ventouse

all forceps

breech

svd

First births <28 weeks



First births at term

All singletons

Per

cent

age




11Births in Scotland


Hospital-level variation

Table 6a shows the rates of the various modes of delivery for individual hospitals based on aggregate data for the most recent five-year period (1996-2000). To minimise the effect of differing case-mix on comparisons, the rates shown are based only on singleton, term, first births with cephalic presentations. In order that comparisons are based on reasonable numbers of cases, only hospitals with at least 2500 relevant deliveries during the five-year period are included.


Singleton, term, first births, cephalic presentations by hospital and mode of delivery, 1996-2000 (aggregated) (only hospitals with ≥2500 births in the period 1996-2000 have been included)


svd breech1 all forceps ventouse elcs emcs not known TotalAberdeen Maternity 4 663 3 1 331 1 517 69 1 747 3 9 333Glasgow Maternity 4 929 0 1 390 619 119 1 311 0 8 368Ninewells 3 159 5 1 526 498 60 742 2 5 992Queen Mothers 3 473 1 1 571 493 88 1 165 1 6 792SMMP 6 522 1 1 996 975 114 2 011 0 11 619

Ayrshire Central 4 740 1 1 081 238 117 1 194 0 7 371Bellshill Maternity 4 529 1 861 444 145 897 2 6 879Cresswell Maternity 1 897 1 105 154 48 382 0 2 587Falkirk and District Royal 1 974 0 394 334 20 481 1 3 204Forth Park 4 252 0 514 392 41 853 0 6 052Law Hospital 1 952 0 129 271 34 420 0 2 806Raigmore 2 272 0 371 502 35 674 0 3 854Royal Alexandra 2 163 0 638 528 110 845 1 4 285Southern General 2 971 1 601 477 63 653 0 4 766St Johns 3 163 1 450 290 65 668 0 4 637Stirling Royal Infirmary 2 203 0 324 254 19 396 0 3 196Total 54 862 15 13 282 7 986 1 147 14 439 10 91 741


Aberdeen Maternity 50.0 0.0 14.3 16.3 0.7 18.7 0.0 100.0Glasgow Maternity 58.9 - 16.6 7.4 1.4 15.7 - 100.0Ninewells 52.7 0.1 25.5 8.3 1.0 12.4 0.0 100.0Queen Mothers 51.1 0.0 23.1 7.3 1.3 17.2 0.0 100.0SMMP 56.1 0.0 17.2 8.4 1.0 17.3 - 100.0

Ayrshire Central 64.3 0.0 14.7 3.2 1.6 16.2 - 100.0Bellshill Maternity 65.8 0.0 12.5 6.5 2.1 13.0 0.0 100.0Cresswell Maternity 73.3 0.0 4.1 6.0 1.9 14.8 - 100.0Falkirk & District Royal 61.6 - 12.3 10.4 0.6 15.0 0.0 100.0Forth Park 70.3 - 8.5 6.5 0.7 14.1 - 100.0

Law Hospital 69.6 - 4.6 9.7 1.2 15.0 - 100.0

Raigmore 59.0 - 9.6 13.0 0.9 17.5 - 100.0

Royal Alexandra 50.5 - 14.9 12.3 2.6 19.7 0.0 100.0

Southern General 62.3 0.0 12.6 10.0 1.3 13.7 - 100.0

St Johns 68.2 0.0 9.7 6.3 1.4 14.4 - 100.0

Stirling Royal Infirmary 68.9 - 10.1 7.9 0.6 12.4 - 100.0

Total 59.8 0.0 14.5 8.7 1.3 15.7 0.0 100.0

6a

1 Breech deliveries represent cases where the presentation was misdiagnosed or changed during labour





The hospital-level variation in Caesarean delivery rates (from 13.0% in Stirling Royal Infirmary to 22.3% in the Royal Alexandra, Paisley) has been highlighted in our previous SPCERH publications.4,5 There are also hospital-level variations in rates of operative vaginal delivery – the topic of this report. During the five-year period, the overall operative vaginal delivery rate (forceps plus ventouse) among the hospitals studied was 23.2%. The equivalent rate for individual hospitals ranged from 10.0% (95% CI, 8.9-11.3) at Cresswell, Dumfries to 33.8% (95% CI, 32.5-35.1) at Ninewells, Dundee.

The proportional use of forceps and ventouse for instrumental delivery also varied greatly among individual hospitals. For example, in Ayrshire Central, only 18% of operative vaginal deliveries were conducted using the ventouse; in contrast, in Law Hospital (now incorporated within Wishaw hospital) 68% of all instrumental deliveries involved the ventouse.

Variations at hospital level may be explained by a range of factors including the preferences of obstetricians and case mix. In Table 6a, we have attempted to reduce the effects of case mix by restricting analysis to singleton, cephalic, first births at term. Preliminary analyses demonstrated that increasing maternal age is associated with an increasing rate of operative vaginal delivery. Table 6b summarises the same data as Table 6a but includes indirect standardisation for maternal age – further reducing the effects of case-mix on hospital-level variation. After standardising for maternal age, rates of operative vaginal delivery in individual hospitals range from 44% of the expected rate (Cresswell Maternity) to 150% of the expected rate (Ninewells). Thus, there are major differences among Scottish maternity units in the rates of operative vaginal delivery which cannot readily be explained by case-mix differences.

OVD’s 1 % OVD 1,2

Actual Expected All Modes Actual Expected SRR 3

Aberdeen Maternity 2 848 2 228 9 333 30.5 23.9 127.9Glasgow Maternity 2 009 1 894 8 368 24.0 22.6 106.1Ninewells 2 024 1 350 5 992 33.8 22.5 149.9Queen Mothers 2 064 1 623 6 792 30.4 23.9 127.1SMMP 2 971 2 808 11 619 25.6 24.2 105.8

Ayrshire Central 1 319 1 650 7 371 17.9 22.4 79.9Bellshill Maternity 1 305 1 562 6 879 19.0 22.7 83.6Cresswell Maternity 259 589 2 587 10.0 22.8 44.0Falkirk and District Royal 578 736 3 196 18.1 23.0 78.5Forth Park 906 1 356 6 052 15.0 22.4 66.8Law Hospital 400 641 2 806 14.3 22.9 62.4Raigmore 873 891 3 854 22.7 23.1 98.0Royal Alexandra 1 166 998 4 285 27.2 23.3 116.9Southern General 1 078 1 109 4 766 22.6 23.3 97.2St Johns 740 1 088 4 637 16.0 23.5 68.1Stirling Royal Infirmary 728 745 3 204 22.7 23.3 97.7Total 21 268 21 268 91 741 23.2 23.2 100.0

Singleton, term, first births, cephalic presentations by hospital and mode of delivery, 1996-2000 (aggregated) (only hospitals with ≥2500 births in the period 1996-2000 have been included) standardised for maternal age

6b

1 All forceps and ventouse. 2 Percentage of all modes. 3 Indirect Standardised Ratio, age.






Neonatal outcomes

MortalityTable 7 and Figure 4 summarise rates of neonatal death among singleton, term infants delivered by the various different modes for the 10-year period 1991-2000. Numbers and denominators are also available in Table 7a and Table 7c respectively. Unlike the time-trend data presented above, these data are not restricted to births where the fetus was recorded as ‘cephalic’ at the onset of labour; they include known breech presentations also.

Based on these data, the neonatal death rates (per 1000 live births) associated with each mode of delivery were as follows:

• Spontaneous vertex delivery 0.9 (95% CI, 0.8-1.0) • Vaginal breech delivery 10.1 (95% CI, 5.9-16.2) • Forceps delivery 1.6 (95% CI, 1.2-2.0) • Ventouse delivery 0.8 (95% CI, 0.4-1.3) • Elective Caesarean delivery 2.1 (95% CI, 1.7-2.7) • Emergency Caesarean delivery 3.1 (95% CI, 2.6-3.6)

These figures show that both forceps and ventouse deliveries are associated with neonatal death rates which are similar to the rate for spontaneous vertex deliveries. However, both elective and emergency Caesarean deliveries, and particularly vaginal breech deliveries, are associated with neonatal death rates significantly higher than those for spontaneous vertex or for instrumental cephalic deliveries. Of course, in a cohort study of this type, the higher neonatal death rates associated with certain forms of delivery may be causally related to the underlying condition which dictated the mode of delivery or to patient characteristics such a deprivation, rather than to the mode of delivery itself. Our finding of increased neonatal mortality associated with vaginal breech delivery is entirely compatible with the findings of the recent international term breech trial. 11

Figure 4 Singleton, term neonatal deaths by year and mode of delivery, 1991-2000 (aggregated)

0

2

4

6

8

10emergency CS

elective CS

ventouse

all forceps

breech

svd

Late neonatal deathsEarly neonatal deaths

Rat

e pe

r si

ngle

ton,

term

, liv

e bi

rth

Source: ISD (Scotland), Scottish Stillbirth and Infant Death Survey





Singleton, term neonatal deaths by year and mode of delivery, 1991-2000 - numbers

Mode of deliveryEarly neonatal deaths

svd breechall

forceps ventouse elcs emcsnot

known Total1991 24 3 9 0 0 21 0 571992 27 4 10 2 13 12 0 681993 36 3 4 1 11 10 0 651994 11 2 6 2 5 8 0 341995 24 0 7 0 7 12 0 501996 19 1 1 1 4 16 0 421997 20 1 5 1 2 16 0 451998 18 0 4 0 1 11 0 341999 11 0 4 2 3 9 0 29

2000 17 0 4 0 2 14 0 37Total 207 14 54 9 48 129 0 461

Late neonatal deaths

svd breechall

forceps ventouse elcs emcsnot

known Total1991 16 1 3 0 0 9 0 291992 22 0 3 1 5 1 0 321993 12 1 1 0 2 1 0 171994 23 1 1 1 4 4 1 351995 10 0 4 1 2 5 0 221996 12 0 4 0 4 4 0 241997 14 0 1 0 1 2 0 181998 16 0 0 0 3 1 1 211999 9 0 0 2 0 1 0 122000 11 0 0 1 2 2 2 18Total 145 3 17 6 23 30 4 228

7a

Sources: ISD (Scotland) Scottish Stillbirth and Infant Death Survey, SMR02





Singleton, term neonatal deaths by year and mode of delivery, 1991-2000 - rates1

Mode of deliveryEarly neonatal deaths

svd breech all forceps ventouse elcs emcs not known Total1991 0.5 10.8 1.4 - - 4.2 - 0.91992 0.6 15.7 1.6 1.9 4.0 2.4 - 1.11993 0.8 13.8 0.8 0.7 3.3 2.0 - 1.11994 0.3 11.4 1.3 1.1 1.5 1.6 - 0.61995 0.6 - 1.6 - 2.2 2.5 - 0.91996 0.5 6.0 0.3 0.5 1.2 3.3 - 0.81997 0.5 7.0 1.2 0.4 0.6 3.1 - 0.81998 0.5 - 1.1 - 0.3 2.0 - 0.71999 0.3 - 1.1 0.8 0.8 1.6 - 0.62000 0.5 - 1.2 - 0.6 2.5 - 0.8Total 0.5 8.3 1.2 0.5 1.4 2.5 - 0.8

Late neonatal deathssvd breech all forceps ventouse elcs emcs not known Total

1991 0.4 3.6 0.5 - - 1.8 - 0.51992 0.5 - 0.5 0.9 1.5 0.2 - 0.51993 0.3 4.6 0.2 - 0.6 0.2 - 0.31994 0.6 5.7 0.2 0.5 1.2 0.8 66.7 0.61995 0.3 - 0.9 0.5 0.6 1.0 - 0.41996 0.3 - 1.0 - 1.2 0.8 - 0.51997 0.4 - 0.2 - 0.3 0.4 - 0.31998 0.4 - - - 0.9 0.2 166.7 0.41999 0.3 - - 0.8 - 0.2 - 0.22000 0.4 - - 0.4 0.6 0.4 400.0 0.4Total 0.4 1.8 0.4 0.3 0.7 0.6 34.2 0.4

Mode of deliverysvd breech all forceps ventouse elcs emcs not known Total

1991 45 281 279 6 510 861 3 299 5 014 13 61 2571992 43 569 255 6 221 1 060 3 279 4 899 13 59 2961993 42 441 218 5 331 1 415 3 284 5 014 30 57 7331994 40 896 176 4 775 1 855 3 264 4 854 15 55 8351995 39 990 157 4 294 2 038 3 236 4 842 8 54 5651996 38 264 168 3 875 2 201 3 241 4 861 8 52 6181997 38 639 143 4 054 2 326 3 470 5 116 11 53 7591998 36 363 93 3 788 2 578 3 504 5 578 6 51 9101999 33 931 107 3 628 2 638 3 561 5 583 8 49 4562000 31 103 86 3 243 2 571 3 402 5 610 5 46 020

Total 390 477 1 682 45 719 19 543 33 540 51 371 117 542 449

Singleton, term, live births by year and mode of delivery, 1991-2000Denominator data for 7a and 7b

7b

7c

Sources: Scottish Stillbirth and Infant Death SurveyISD (Scotland), SMR2/SMR02





Health service utilisation

Postpartum hospital stayThe average length of postpartum stay has decreased over time. Tables 8, 9, 10 and 11 and Figure 5 summarise data on length of postpartum stay over the 20 year period 1981 to 2000. Data are restricted to first births with cephalic presentations at term. Figure 5 shows the distribution of lengths of postpartum stay for each of the five-year time periods during 1981-2000. The distribution curves reflect the shift in mean length of stay from 5.4 days in 1981-85 to 3.4 days in 1996-2000.

Figure 6 summarises the mean length of stay for women experiencing different modes of delivery in each five-year time period. Again, data are restricted to first births with cephalic presentations at term. The Figure demonstrates the steady fall over time in postpartum stay associated with all modes of delivery. At each time point, spontaneous vertex delivery is associated with the shortest mean postpartum stay, Caesarean section with the longest, and instrumental vaginal deliveries with an intermediate length of stay. At each time point, there is little difference between elective and emergency Caesarean sections and between forceps and ventouse deliveries in terms of length of stay. Paradoxically, over the entire 20 year period, ventouse delivery appears to be associated with the shortest mean length of stay (3.8 days). This is because a very high proportion of ventouse deliveries took place in the more recent years, when postpartum stay was shorter for all modes of delivery.

Over the most recent five-year period (1996-2000), for primigravid women with cephalic presentations at term, Caesarean sections accounted for 16% of all deliveries, but for 23% of total postpartum bed utilisation. In contrast, instrumental vaginal deliveries accounted for 23% of all births and for 23% of bed utilisation.

Singleton, term, first births, cephalic presentations by postnatal stay and mode of delivery, 1981-1985 (aggregated) 8


svd breech1 all forceps ventouse elcs emcs not known Totalpostnatal

stay0 515 0 107 0 1 20 1 6441 3 866 1 471 5 3 14 0 4 3602 5 205 2 1 329 12 4 42 0 6 5943 4 704 1 1 205 31 13 179 0 6 1334 12 174 0 2 979 118 37 338 4 15 6505 23 798 1 8 008 198 49 430 7 32 4916 18 669 1 8 008 149 121 993 8 27 949

7-9 11 073 1 5 956 195 765 7 158 6 25 15410-12 813 0 564 17 252 1 843 1 3 490

13+ 220 0 178 2 42 331 1 774Total 81 037 7 28 805 727 1 287 11 348 28 123 239


postnatal stay

0 0.6 - 0.4 - 0.1 0.2 3.6 0.51 4.8 14.3 1.6 0.7 0.2 0.1 - 3.52 6.4 28.6 4.6 1.7 0.3 0.4 - 5.43 5.8 14.3 4.2 4.3 1.0 1.6 - 5.04 15.0 - 10.3 16.2 2.9 3.0 14.3 12.75 29.4 14.3 27.8 27.2 3.8 3.8 25.0 26.46 23.0 14.3 27.8 20.5 9.4 8.8 28.6 22.7

7-9 13.7 14.3 20.7 26.8 59.4 63.1 21.4 20.410-12 1.0 - 2.0 2.3 19.6 16.2 3.6 2.8

13+ 0.3 - 0.6 0.3 3.3 2.9 3.6 0.6Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

1 Breech deliveries represent cases where the presentation was misdiagnosed or changed during labour Source: ISD (Scotland), SMR02





Singleton, term, first births, cephalic presentations by postnatal stay and mode of delivery, 1991-1995 (aggregated)



svd breech1 all forceps ventouse elcs emcs not known Totalpostnatal stay

0 1 170 0 239 13 3 13 0 1 4381 3 642 1 835 24 1 27 1 4 5312 4 727 1 1 347 46 9 108 1 6 2393 10 786 0 2 484 258 12 282 13 13 8354 23 922 0 6 524 528 43 450 22 31 4895 24 443 2 8 372 546 104 1 344 12 34 8236 9 485 1 4 015 217 248 3 598 4 17 568

7-9 4 243 1 2 258 182 552 6 559 8 13 80310-12 440 0 281 14 79 711 3 1 528

13+ 165 0 87 9 21 212 1 495Total 83 023 6 26 442 1 837 1 072 13 304 65 125 749

Percentagespostnatal stay

0 1.4 - 0.9 0.7 0.3 0.1 - 1.11 4.4 16.7 3.2 1.3 0.1 0.2 1.5 3.62 5.7 16.7 5.1 2.5 0.8 0.8 1.5 5.03 13.0 - 9.4 14.0 1.1 2.1 20.0 11.04 28.8 - 24.7 28.7 4.0 3.4 33.8 25.05 29.4 33.3 31.7 29.7 9.7 10.1 18.5 27.76 11.4 16.7 15.2 11.8 23.1 27.0 6.2 14.0

7-9 5.1 16.7 8.5 9.9 51.5 49.3 12.3 11.010-12 0.5 - 1.1 0.8 7.4 5.3 4.6 1.2

13+ 0.2 - 0.3 0.5 2.0 1.6 1.5 0.4Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0



0 846 0 104 35 3 41 0 1 0291 3 160 0 599 166 8 71 0 4 0042 9 274 0 1 500 481 19 187 2 11 4633 22 546 0 4 665 1 387 26 364 4 28 9924 25 428 1 7 829 1 697 113 1 578 14 36 6605 11 332 0 4 540 933 269 4 401 9 21 4846 3 214 0 1 556 351 312 4 430 2 9 865

7-9 2 131 0 1 112 288 244 2 939 4 6 71810-12 274 0 129 30 38 336 1 808

13+ 88 0 56 7 17 120 0 288Total 78 293 1 22 090 5 375 1 049 14 467 36 121 311


0 1.1 - 0.5 0.7 0.3 0.3 - 0.81 4.0 - 2.7 3.1 0.8 0.5 - 3.32 11.8 - 6.8 8.9 1.8 1.3 5.6 9.43 28.8 - 21.1 25.8 2.5 2.5 11.1 23.94 32.5 100.0 35.4 31.6 10.8 10.9 38.9 30.25 14.5 - 20.6 17.4 25.6 30.4 25.0 17.76 4.1 - 7.0 6.5 29.7 30.6 5.6 8.1

7-9 2.7 - 5.0 5.4 23.3 20.3 11.1 5.510-12 0.3 - 0.6 0.6 3.6 2.3 2.8 0.7

13+ 0.1 - 0.3 0.1 1.6 0.8 - 0.2Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

10

9









0 1 133 1 122 77 3 45 1 1 3821 6 221 2 836 595 16 117 1 7 7882 18 287 4 2 822 1 908 22 462 1 23 5063 21 768 3 4 823 2 961 154 1 767 2 31 4784 10 873 2 3 592 2 006 479 5 373 3 22 3285 4 007 4 1 499 957 342 5 250 2 12 0616 1 609 1 767 410 122 1 866 1 4 776

7-9 1 269 0 573 342 115 1 235 1 3 53510-12 217 0 92 48 21 223 0 601

13+ 80 1 43 14 14 84 0 236Total 65 464 18 15 169 9 318 1 288 16 422 12 107 691


0 1.7 5.6 0.8 0.8 0.2 0.3 8.3 1.31 9.5 11.1 5.5 6.4 1.2 0.7 8.3 7.22 27.9 22.2 18.6 20.5 1.7 2.8 8.3 21.83 33.3 16.7 31.8 31.8 12.0 10.8 16.7 29.24 16.6 11.1 23.7 21.5 37.2 32.7 25.0 20.75 6.1 22.2 9.9 10.3 26.6 32.0 16.7 11.26 2.5 5.6 5.1 4.4 9.5 11.4 8.3 4.4

7-9 1.9 - 3.8 3.7 8.9 7.5 8.3 3.310-12 0.3 - 0.6 0.5 1.6 1.4 - 0.6

13+ 0.1 5.6 0.3 0.2 1.1 0.5 - 0.2Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0


Figure 5 - Singleton, term, first births, cephalic presentations by postnatal stay, 5-year periods

11

0

5

10

15

20

25

30

351996-2000

1991-1995

1986-1990

1981-1985

13+10-127-96543210

Per

cent

age

Postnatal stay

1 Breech deliveries represent cases where the presentation was misdiagnosed or changed during labour Source: ISD (Scotland), SMR02






Maternal morbidity

Third degree tearTable 12b summarises rates of the complication of third degree perineal tear, as coded on SMR02, for different modes of delivery over the ten-year period 1991-2000. Numbers and denominators are also available in Table 12a and Table 12c respectively. As above, these data are restricted to singleton, first births at term. However, Table 12c is not restricted to cephalic presentations and therefore includes data on all vaginal breech deliveries (545 over the 10 years), not just the small number included in the data discussed above (19 over the 10 years) where presentation was misdiagnosed or changed in labour.

Over the 10-year period, the rates of third degree tear associated with the different modes of vaginal delivery were as follows:

• Spontaneous vertex delivery 5.4/1000 95% CI, 5.1-5.8 • Forceps deliveries 16.1/1000 95% CI, 14.8-17.4 • Ventouse deliveries 9.9/1000 95% CI, 8.3-11.6 • Vaginal breech deliveries 1.8/1000 95% CI, 0.0-10.2

These data show that both forceps and ventouse deliveries are associated with significantly higher rates of third degree tear than spontaneous delveries. Also, forceps deliveries have a significantly higher rate than ventouse deliveries. Of course, these data have been collected through a cohort study, rather than through a randomised trial and it may be the obstetric problems which prompted the use of forceps rather than ventouse which explain the higher rate of tears, rather than the use of forceps per se. Nevertheless, this finding is compatible with that of a Cochrane Review which addressed Vacuum extraction versus forceps for assisted vaginal delivery6 and found a significantly reduced risk of maternal trauma with the vacuum.

Figure 6 - Singleton, term, first births, cephalic presentations, average postnatal stay, 5-year periods

0

1

2

3

4

5

6

7

8

9

emcs

elcs

ventouse

all forceps

svd

1996-20001991-19951986-19901981-1985

Leng

th o

f sta

y






Mode of delivery Total with 3rdsvd breech all forceps ventouse elcs emcs not known degree tear

1991 78 0 43 2 - - - 1231992 69 0 44 2 - - - 1151993 99 0 50 3 - - 2 1541994 101 0 54 8 - - - 1631995 100 0 49 17 - - - 1661996 52 0 60 21 - - - 1331997 33 0 63 14 - - - 1101998 83 1 71 20 - 1 - 1761999 87 0 80 27 - 1 - 1952000 85 0 95 33 - - - 213Total 787 1 609 147 - 2 2 1 548

Singleton deliveries, first births only, at term (37 weeks and above), with third degree tear1, 1991-2000 - numbers12a

12b

12c

Mode of delivery

svd breech all forceps ventouse elcs emcs not known Total

1991 4.5 - 7.8 3.0 - - - 4.41992 4.3 - 8.5 2.5 - - - 4.31993 6.2 - 11.4 2.8 - - 133.3 6.01994 6.8 - 13.6 5.8 - - - 6.71995 6.8 - 13.7 10.8 - - - 6.91996 3.7 - 18.7 12.3 - - - 5.71997 2.3 - 18.8 8.0 - - - 4.61998 6.2 29.4 22.9 10.3 - 0.3 - 7.61999 6.8 - 26.7 13.2 - 0.3 - 8.62000 7.5 - 35.0 16.9 - - - 10.3Total 5.4 1.8 16.1 9.9 - 0.1 35.1 6.4

Singleton deliveries, first births only, at term (37 weeks and above), with third degree tear1, 1991-2000 - rates2

1 Third degree tears identified in any position (1 to 6); ICD9 -664.2; ICD10 O70.2; also any hard-coded on the record (tear=3).

2 Rates per 1000 singleton, term, first births.

Mode of delivery

svd breech all forceps ventouse elcs emcs not known Total

1991 17 307 88 5 479 657 841 3 450 8 27 8301992 16 230 102 5 154 786 872 3 410 2 26 5561993 15 858 72 4 384 1 074 858 3 397 15 25 6581994 14 893 49 3 957 1 391 839 3 217 11 24 3571995 14 781 42 3 579 1 574 792 3 291 5 24 0641996 14 051 48 3 210 1 706 852 3 262 6 23 1351997 14 263 50 3 358 1 756 859 3 392 3 23 6811998 13 419 34 3 103 1 949 839 3 830 1 23 1751999 12 778 34 2 991 2 038 865 3 872 5 22 5832000 11 405 26 2 713 1 957 809 3 771 1 20 682Total 144 985 545 37 928 14 888 8426 34 892 57 241 721

Singleton deliveries, first births only, at term (37 weeks and above), 1991-2000Denominator data for 12a and 12b






Mode of first deliveryNumbers

Years between first delivery and second

delivery

svd breech ovd cs not known Total

1-2 3 151 44 883 601 12 4 6912-3 3 884 29 1 232 831 11 5 9873-4 2 412 20 789 566 10 3 7974-5 1 334 8 427 313 4 2 0865-6 763 8 249 195 3 1 2186-7 552 3 155 102 1 8137-8 330 2 115 92 1 5408+ 123 4 43 25 1 196

All first-born singletons (born in 1987)

18 280 178 5 784 4 463 63 28 768

Percentages


delivery


0-1 1.0 3.9 0.8 0.3 0.0 0.91-2 17.2 24.7 15.3 13.5 19.0 16.32-3 21.2 16.3 21.3 18.6 17.5 20.83-4 13.2 11.2 13.6 12.7 15.9 13.24-5 7.3 4.5 7.4 7.0 6.3 7.35-6 4.2 4.5 4.3 4.4 4.8 4.26-7 3.0 1.7 2.7 2.3 1.6 2.87-8 1.8 1.1 2.0 2.1 1.6 1.98+ 0.7 2.2 0.7 0.6 1.6 0.7

Cumulative percentages


delivery


0-1 1.0 3.9 0.8 0.3 0.0 0.91-2 18.3 28.7 16.0 13.8 19.0 17.22-3 39.5 44.9 37.3 32.4 36.5 38.03-4 52.7 56.2 51.0 45.1 52.4 51.24-5 60.0 60.7 58.4 52.1 58.7 58.45-6 64.2 65.2 62.7 56.5 63.5 62.76-7 67.2 66.9 65.3 58.7 65.1 65.57-8 69.0 68.0 67.3 60.8 66.7 67.48+ 69.7 70.2 68.1 61.4 68.3 68.1

Source: ISD(Scotland), SMR02, Linked database

Singleton deliveries, first births born in 1987, subsequent fertility to 199613





Subsequent fertilityPrevious work from the Aberdeen Maternal and Neonatal Databank 7 relating to the time period 1964-1983 showed that women whose first birth was by Caesarean section were less likely to have a subsequent delivery than those who had a spontaneous first birth. Women delivered by forceps were an intermediate group. From the SMR02 dataset, we identified a cohort of 28768 women who had their first birth in 1987. Table 13 summarises the modes of delivery of these women and shows the cumulative percentage of women who had a second delivery for each year of follow-up to a maximum of eight.

The cumulative percentages, year on year, having a second delivery for women whose first delivery was spontaneous vertex, operative vaginal or Caesarean are summarised in Figure 7. This Figure shows the same pattern of subsequent fertility as the Aberdeen study. The differences in subsequent fertility demonstrated may be due to the obstetric complications or patient characteristics which determined the mode of first delivery, rather than to the mode of delivery per se.

Figure 7 - Singleton deliveries, first births born in 1987, subsequent fertility to 1995

0

10

20

30

40

50

60

70

80

90

100

cs

ovd

svd

8+7-86-75-64-53-42-31-20-1

Years between first and second delivery

Cum

ulat

ive

perc

enta

ge






Urinary and anal incontinenceUrinary and anal incontinence are relatively common problems among women in the reproductive and postreproductive years. Previous work has indicated that obstetric factors, including mode of delivery, are associated with these conditions.8,9,10 A data linkage study examining obstetric risk factors for anal incontinence has been undertaken by Tierney JP, Boyd J and Greer I. Their findings are summarised here.

The SMR01 dataset for 1981 to 1999 was searched for specific OPCS4 and ICD10 codes in order to identify women who had undergone surgery for anal incontinence. Records for 12,368 women who had undergone these procedures were identified.

The SMR02 dataset for 1981 to 1985 was searched in order to identify women who had their last delivery during this time period. Records for 156,707 such women were identified.

Standard probability matching techniques were used with these two sets of records to identify any women who had their last delivery during the period of interest and had surgery for anal incontinence during the follow-up period of 14-18 years. Records for 274 such women were identified. In examining associations with anal incontinence, these 274 women were compared with the remaining 156,433 women (those who had their last delivery during the period of interest, but had no record of subsequent surgery for anal incontinence).

The overall risk of a woman requiring surgery for anal incontinence during a follow-up period of 14-18 years after her last delivery was 0.175% (274/156,707). Univariate and multivariate logistic regression showed that only two obstetric variables were significantly and independently associated with risk of anal incontinence:

• total previous pregnancies: OR for parity >=4 compared to parity zero, 1.94 [95% CI, 1.19-3.17]

• age at last delivery: OR for age >35 years compared to <25 years, 1.96 [95% CI, 1.19-2.96].

In this study, anal incontinence requiring surgery was found to be rare and no significantly increased risk was associated with operative vaginal delivery when compared to Caesarean delivery. (Rate of anal incontinence after Caesarean delivery, 0.15%; rate after forceps delivery, 0.24%; OR, 1.60; 95% CI, 0.86-2.98).





Chapter references

1 Information & Statistics Division. Births in Scotland 1976-1995. Births in Scotland Publication Series 1. 1997. Edinburgh, ISD, Common Services Agency, Scottish Health Service.

2 Information & Statistics Division. Small Babies in Scotland: a ten year overview 1987-1996. Births in Scotland Publication Series 2, 1998.

3 SPCERH and ISD. Babies with anomalies: a Scottish overview. Births in Scotland Publication Series 3. 2001. Edinburgh, SPCERH and ISD.

4 SPCERH. Caesarean section in Scotland: current practice and recommendations for the future. 1999. Aberdeen, SPCERH Newsletter.

5 SPCERH. Expert Advisory Group on Caesarean Section in Scotland: Report and recommendations to the Chief Medical Officer of the Scottish Executive Health Department. 2001. available online at: www.show.scot.nhs.uk/crag.

6 Johanson RB,.Menon V. Vacuum extraction versus forceps for assisted vaginal delivery (Cochrane Review). The Cochrane Library (Issue 2).Oxford: Update Software 2002.

7 Hall M.H., Campbell DM, Fraser C, Lemon J. Mode of delivery and future fertility. BJOG 1989;96:1297-303.

8 Viktrup L,.Lose G. The risk of stress incontinence 5 years after first delivery. Am J Obstet Gynecol 2001;185:87.

9 Arya LA, Jackson ND, Myers DL, Verma A. Risk of new-onset urinary incontinence after forceps and vacuum delivery in primiparous women. Am J Obstet Gynecol 2001;185:1324.

10 Meyer S, Hohlfeld P, Achtari C, Russolo A, DeGrandi P. Birth trauma: short and long term effects of forceps delivery compared with spontaneous delivery on various pelvic floor parameters. BJOG 2000;107:1360-5.

11 Hannah ME, Hannah WJ, Hewson SA, Hodnett ED, Saigal S, Willan AR et al. Planned caesarean section versus planned vaginal birth for breech presentation at term: a randomised multicentre trial. Lancet 2000; 356: 1375-83

Information & Statistics Division. Births in Scotland 1976-1995. Births in Scotland Publication Series 1. 1997. Edinburgh, ISD, Common Services Agency, Scottish Health Service.

Information & Statistics Division. Small Babies in Scotland: a ten year overview 1987-1996. Births in Scotland Publication Series 2, 1998.

SPCERH and ISD. Babies with anomalies: a Scottish overview. Births in Scotland Publication Series 3.

SPCERH. Caesarean section in Scotland: current practice and recommendations for the future. 1999.

Information & Statistics Division. Births in Scotland 1976-1995. Births in Scotland Publication Series 1. 1997. Edinburgh, ISD, Common Services Agency, Scottish Health Service.

Information & Statistics Division. Small Babies in Scotland: a ten year overview 1987-1996. Births in Scotland Publication Series 2, 1998.

SPCERH and ISD. Babies with anomalies: a Scottish overview. Births in Scotland Publication Series 3.

SPCERH. Caesarean section in Scotland: current practice and recommendations for the future. 1999.




For the last three years, we have included a clinical Chapter, in addition to the traditional statistics, within the SPIMMR. The aim of these Chapters is to present a Scottish overview of an important clinical topic based on the data routinely collected by ISD. This fourth annual clinical Chapter focuses on multiple pregnancies. The following data on the incidence, associations and sequelae of multiple pregnancies are drawn from ISD’s SMR02 and SSBIDS datasets and from the General Register Office (Scotland).

Background

Biologically, multiple pregnancy occurs in two ways – by splitting of a single fertilised egg (monozygous, MZ) or by fertilisation of multiple eggs (dizygous, DZ). It is long-established that the incidence of monozygous twinning is relatively constant worldwide, and over time, at 3.5 per 1000 births.6 Dizygous twinning rates vary widely and are affected by age, parity, race, and the use of assisted reproduction techniques.

In this Chapter, we present Scottish data to examine time trends in multiple pregnancy, associations described by others, and outcomes for babies and mothers.

Incidence and time trends in Scotland

Table 14a and Figure 8a are based on GRO(S) data and show the time trend of rates of twin births and of higher order multiple births since 1855. Although there is a clear upward trend in the multiple pregnancy rate in recent years, rates are no higher now than at previous peaks in the 1920’s and 1950’s. Table 14b and Figure 8b provide a more detailed picture of the trend since 1981.


26 Births in Scotland 27Births in Scotland


Number and percentage of multiple births - 1855-2000

All Singletons Twins Triplets+ All multiples % multiple All babies maternities births 1855-60 101 148 99 850 1 282 16 1 298 1.28 102 462 1861-65 108 440 107 129 1 298 13 1 311 1.21 109 764 1866-70 112 975 111 569 1 393 13 1 406 1.24 114 394 1871-75 118 934 117 505 1 416 13 1 429 1.20 120 376 1876-80 124 628 123 184 1 430 14 1 444 1.16 126 086 1881-85 124 964 123 533 1 417 14 1 431 1.15 126 409 1886-90 122 573 121 182 1 378 13 1 391 1.13 123 977 1891-95 124 354 122 921 1 420 13 1 433 1.15 125 800 1896-1900 128 712 127 231 1 465 16 1 481 1.15 130 209

1901-05 130 766 129 150 1 599 17 1 616 1.24 132 399 1906-10 127 350 125 727 1 609 14 1 623 1.27 128 987 1911-15 119 086 117 533 1 538 15 1 553 1.30 120 654 1916-20 108 239 106 738 1 491 10 1 501 1.39 109 750 1921-25 110 766 109 297 1 459 10 1 469 1.33 112 245 1926-30 95 424 94 185 1 228 11 1 239 1.30 96 674 1931-35 88 206 87 118 1 076 12 1 088 1.23 89 306 1936-40 86 600 85 474 1 118 8 1 126 1.30 87 734 1941-45 93 693 92 415 1 263 15 1 278 1.36 94 986 1946-50 102 822 101 392 1 413 17 1 430 1.39 104 269

1951-55 92 460 91 176 1 272 12 1 284 1.39 93 756 1956-60 99 657 98 355 1 291 11 1 302 1.31 100 970 1961-65 103 399 102 168 1 219 12 1 231 1.19 104 642 1966-70 93 445 92 452 983 10 993 1.06 94 448 1971-75 75 717 74 960 751 6 757 1.00 76 480 1976-80 65 661 65 041 614 6 620 0.94 66 287 1981-85 66 149 65 494 648 7 655 0.99 66 811 1986-90 65 159 64 436 711 12 723 1.11 65 894 1991-95 63 137 62 340 778 19 797 1.26 63 954 1996-2000 56 367 55 572 775 20 795 1.41 57 183

14a

Source: General Register Office (Scotland)

Figure 8a - Percentage of multiple births - historic trend (1855-2000)


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Number and percentage of multiple births - 1981-2000

All Singletons Twins Triplets+ All multiples % multiple All babies maternities births 1981 68 865 68 247 611 7 618 0.90 69 490 1982 65 963 65 350 607 6 613 0.93 66 582 1983 64 776 64 097 677 2 679 1.05 65 457 1984 64 800 64 125 665 10 675 1.04 65 485 1985 66 342 65 651 682 9 691 1.04 67 042

1986 65 456 64 725 721 10 731 1.12 66 197 1987 65 839 65 108 721 10 731 1.11 66 580 1988 65 843 65 127 706 10 716 1.09 66 569 1989 63 092 62 400 677 15 692 1.10 63 799 1990 65 557 64 809 731 17 748 1.14 66 322

1991 66 636 65 903 709 24 733 1.10 67 393 1992 65 308 64 486 807 15 822 1.26 66 145 1993 62 946 62 156 780 10 790 1.26 63 746 1994 61 225 60 430 778 17 795 1.30 62 037 1995 59 572 58 726 816 30 846 1.42 60 448

1996 58 819 57 990 800 29 829 1.41 59 677 1997 58 926 58 114 791 21 812 1.38 59 759 1998 56 820 55 990 810 20 830 1.46 57 670 1999 54 671 53 921 738 12 750 1.37 55 433 2000 52 599 51 843 737 19 756 1.44 53 374

14b



Figure 8b - Percentage of multiple births - historic trend (1981-2000)

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International Comparisons

On a global scale, there appears to be a 15-fold variation in crude twinning rates – from two to seven per 1000 in low prevalence areas such as Hawaii and Japan to over 20 per 1000 in high prevalence areas such as Nigeria. International variation was reviewed in the Scottish publication Twinning and Twins (1988).6 We are unaware of a more recent comprehensive overview and representative data taken from that publication are summarised in Table15.

International variation in twinning rates(representative data from Twinning and Twins, 1988, ed. MacGillivray, Campbell, Thompson)

Geographical area Time period Twinning rate Per 1000 maternities Low prevalence (2-7/1000) Mexico 1972-78 5.3 Japan 1972-74 5.6 Taiwan 1963-64 5.6 Intermediate prevalence (9-20/1000) Algeria 1963 13.3 South Africa 1963 16.8 Canada 1972-79 9 USA 1978-79 9.6 Brazil 1974-76 16.8 India (South Delhi) 1969-73 9.8 England & Wales** 1998 13.9 Scotland* 2000 14 High prevalence (>20/1000)

Nigeria 1964-68 45.1 Jamaica 1960 25.7

15

Source: General Register Office (Scotland)* Data from ISD ** Data from Birth Counts 7

Antecedents and associations of multiple birth

As indicated above, the descriptive epidemiology of MZ and DZ twinning is very different, with the MZ twinning rate appearing to remain remarkably constant and the DZ rate showing marked variation. MacGillivray, Samphier and Little reviewed various factors reported to affect twinning rates in Twinning and Twins.6 Associations with age, parity, height and social class were examined. In this chapter we explore similar factors using ISD’s SMR02 data.

Maternal ageAs long ago as 1865, Matthews Duncan reported that the highest rate of twinning was in women aged 35 to 39 years and that on each side of this ‘climax of fertility’, the tendency to twinning diminished.8 Subsequent workers have confirmed this finding and it is now generally accepted that DZ twinning rates in Europe, Canada, Japan and among US whites increase with maternal age to a peak in the late 30’s and then decline. In most studies, the form of the curve describing this association is an inverted ‘v’.

Table 16a and Figure 9a summarise the relationship between multiple pregnancy rate and maternal age based on 20year aggregated SMR02 data (1,235,581 maternities). The inverted ‘v’ with a peak at ages 35-39, as described by Matthews Duncan, is confirmed.




SPMMRAG members hypothesised that the relationship between maternal age and multiple pregnancy rate, demonstrated using 20 year aggregated data, might be spurious. Both mean maternal age and multiple pregnancy rate have increased over the 20 years. It is possible therefore that the apparent relationship might be due to confounding by the higher proportion of older mothers in later years. Table 16b and Figure 9b show that mean maternal age has increased steadily over time and that, at all time points, mothers having multiple births have a higher mean age than other mothers. These data indicate that the relationship between maternal age and multiple pregnancy rate is real, and sustained over time.

Number and rate of multiple births per 1000 maternities by maternal age, 1981-2000 (aggregated)

Age group Multiple Total Multiple rate maternities maternities per 1000 maternities 13-15 15 2 640 5.7 16-19 661 107 236 6.2 20-24 2 749 315 452 8.7 25-29 4 984 421 771 11.8 30-34 4 388 280 466 15.6 35-39 1 695 93 508 18.1 40-44 189 13 931 13.6 45+ 7 554 12.6

16a


Figure 9a - Multiple pregnancy rate by maternal age, 1981-2000 (aggregated)


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singleton multiple all births

1981 25.82 27.02 25.83 1982 25.81 26.83 25.82 1983 25.89 27.11 25.90 1984 25.93 27.19 25.95 1985 25.98 26.98 25.99 1986 26.09 27.18 26.10 1987 26.17 27.26 26.19 1988 26.30 27.37 26.31 1989 26.49 27.96 26.51 1990 26.69 28.15 26.71 1991 26.90 28.09 26.91 1992 27.14 28.69 27.16 1993 27.36 28.96 27.38 1994 27.65 28.97 27.66 1995 27.81 29.46 27.83 1996 27.95 29.78 27.98 1997 28.08 30.07 28.10 1998 28.24 29.84 28.26 1999 28.33 30.43 28.35 2000 28.49 30.31 28.51 Total 26.89 28.46 26.91

16b


Figure 9b - Mean maternal age (1981-2000)


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ParityIn the same paper, Matthews Duncan recognised that twinning was commoner in higher parity women.8 Again, his observations have been confirmed by many workers since. Table 17 and Figure 10 summarise the rates of multiple pregnancy for women of different parities based on the SMR02 aggregated data for 1981-2000. There is a statistically significant relationship between parity and multiple pregnancy rate (Chi squared test for trend, 64.9; p<0.0001).

Number and rate of multiple births per 1000 maternities by parity, 1981-2000 (aggregated)

Parity Multiple Total Multiple rate maternities maternities per 1000 maternities 0 6 182 548 457 11.3 1 5 057 426 537 11.9 2 2 300 176 599 13.0 3 743 56 327 13.2 4 273 17 631 15.5 5+ 126 9 644 13.1

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Figure 10 - Multiple pregnancy rate by parity, 1981-2000 (aggregated)


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Maternal heightOver a century ago, Tchouriloff (1877) observed that tall women are more likely to bear twins than small women.9 Again, this historical observation has since been confirmed by many authors. An analysis of Aberdeen city data (1951-1983) in which women were grouped into ‘short’ (<155cm), ‘medium’ and ‘tall’ (≥164cm) categories showed that twinning rates increased directly with height.6 Table 18a and Figure 11a summarise multiple pregnancy rates for women in the same height groupings, based on SMR02 data for 1981 to 2000. These confirm the Aberdeen finding.

As for maternal age, SPMMRAG members hypothesised that the relationship between height and multiple pregnancy rate, demonstrated using 20 year aggregate data, might be spurious. Like age, mean maternal height has increased over the 20 year period and it is possible that the apparent relationship might be due to confounding by the higher proportion of taller mothers in later years. Table 18b and Figure 11b shows that mean maternal height has increased steadily over time and that, at all time points, mothers having multiple births have a greater mean height than other mothers. These data indicate that the relationship between maternal height and multiple pregnancy rate is real, and sustained over time.

Number and rate of multiple births per 1000 maternities by height, 1981-2000 (aggregated)

Multiple Total Multiple rate Height group maternities maternities per 1000 maternities <155 cm 1 420 147 350 9.6 155-163 cm 6 202 567 266 10.9 ≥164 cm 5 241 404 599 13.0

18a


Figure 11a - Multiple pregnancy rate by maternal height, 1981-2000 (aggregated)


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Mean maternal height, 1981-2000

singleton multiple all births 1981 160.12 161.17 160.13 1982 160.25 161.22 160.26 1983 160.41 160.91 160.41 1984 160.60 161.42 160.61 1985 160.69 161.21 160.70 1986 160.82 161.55 160.83 1987 160.94 161.53 160.94 1988 161.05 161.71 161.06 1989 161.28 161.66 161.29 1990 161.52 162.09 161.52 1991 161.66 163.05 161.68 1992 161.87 162.19 161.87 1993 162.02 162.35 162.02 1994 162.19 162.39 162.19 1995 162.32 163.14 162.33 1996 162.53 162.89 162.54 1997 162.60 163.12 162.61 1998 162.71 163.68 162.72 1999 162.90 163.70 162.91 2000 163.06 163.53 163.07 Total 161.48 162.23 161.49

18b


Figure 11b -Mean maternal height (cm) (1981-2000)


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Number and rate of multiple births per 1000 maternities by deprivation category, 1981-2000 (aggregated)

Deprivation Multiple Total Multiple rate category maternities maternities per 1000 maternities

1 942 66 696 14.1 2 2 088 157 552 13.3 3 2 914 247 843 11.8 4 3 411 294 927 11.6 5 2 217 188 391 11.8 6 1 658 144 958 11.4 7 1 086 100 955 10.8

19

Source: ISD (Scotland), SMR2/SMR02

Figure 12 - Multiple pregnancy rate by deprivation category, 1981-2000 (aggregated)


Socio-economic deprivationAn inconsistent picture of the relationship between multiple pregnancy and ‘social class’ emerges from the literature. Table 19 and Figure 12 show the rate of multiple pregnancy among women in different Carstairs deprivation categories (category ‘1’, most affluent; category ‘7’, most deprived).10 There is a statistically significant trend between increasing affluence and increasing rate of multiple pregnancy (chi-squared test for trend, 48.2; p<0.0001).

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Relative importance of associations with multiple pregnancyAn association between risk of mutliple birth and age of mother is well described. It is important not to take the other factors (parity, deprivation and height) in isolation because, although they appear to be associated with the risk of multiple births, these factors are inter-related. For example, parity increases with increasing age, so the demonstrated parity effect may be due to increasing age.

Further analyses were undertaken to determine the relative effects of age, deprivation, parity and height, and the interactions between each effect, on the risk of having a multiple birth over the 20 year period. However, initial results were inconclusive and it was not possible to produce a stable model which took account of all possible interactions between the variables. One of the main problems is that IVF is known to be particularly relevant but could not be included in the analysis because legislation does not permit such data to be held by any other organisation except the Human Fertilisation and Embriology Authority.

Monozygous and dizygous twinning

As indicated earlier, the rate of monozygous twinning is reportedly remarkably constant across time and place, at around 3.5/1000 births. Accurate determination of zygosity requires laboratory investigation. However, a simple mathematical method, Weinberg’s method, allows approximate calculation of numbers of monozygotic and dizygotic twin pairs in a population. Weinberg’s method relies on the assumption that dizygotic twins are equally likely to be of like or unlike sex. Thus, in a population, the number of dizygotic pairs would equal twice the number of unlike sex pairs. The remainder of twin pairs in the population would therefore be monozygotic. Table 20a and Figure 13a show rates of monozygous and dizygous twinning in Scotland over the period 1981 to 2000 calculated using this method.

For the total period, the rate of monozygous twinning is 4.49/1000 maternities – rather higher than the 3.5/1000 quoted in the literature.6 However, the Figure does illustrate the relative constancy of the monozygotic twinning rate year on year. In contrast, the dizygotic rate is increasing steadily, presumably reflecting the impact of increasing maternal age and height and the use of assisted conception techniques, among other factors.

Number and rate of mono- and dizygotic twins by year, 1981-2000

total twins same sex different total dizygotes monozygotes dizygote monozygote

sex maternities rate1 rate1

1981 596 419 177 67 882 354 242 5.21 3.57 1982 609 431 178 64 965 356 253 5.48 3.89 1983 657 484 173 63 946 346 311 5.41 4.86 1984 674 474 200 64 205 400 274 6.23 4.27 1985 680 500 180 64 955 360 320 5.54 4.93

1986 725 523 202 64 695 404 321 6.24 4.96 1987 714 500 214 64 921 428 286 6.59 4.41 1988 710 500 210 65 432 420 290 6.42 4.43 1989 680 493 187 62 980 374 306 5.94 4.86 1990 737 517 220 64 562 440 297 6.82 4.60

1991 706 473 233 66 001 466 240 7.06 3.64 1992 792 543 249 64 222 498 294 7.75 4.58 1993 773 531 242 62 354 484 289 7.76 4.63 1994 775 528 247 60 517 494 281 8.16 4.64 1995 829 565 264 59 033 528 301 8.94 5.10

1996 761 515 246 56 968 492 269 8.64 4.72 1997 795 531 264 58 095 528 267 9.09 4.60 1998 803 553 250 56 262 500 303 8.89 5.39 1999 714 459 255 53 656 510 204 9.50 3.80 2000 679 440 239 49 930 478 201 9.57 4.03

Total 14 409 9 979 4 430 1 235 581 8 860 5 549 7.17 4.49

20a

Source: ISD (Scotland), SMR021 Rates per 1000 maternities.




Figure 13a - Rates of mono- and dizygotic twins (1981-2000)


Table 20b and Figure 13b show the rates of monozygous and dizygous twinning (calculated using Weinberg’s method) for women in different age groups. These data confirm the reported observation that rates of monozygotic twinning are relatively constant, not just over time and place, but for different groups of women. In contrast, the dizygotic twinning rate is shown to account for the overall relationship observed between maternal age and twinning.

Number and rate of mono- and dizygotic twins by maternal age, 1981-2000 (aggregated)

13-15 16-19 20-24 25-29 30-34 35-39 40-44 45+ Total Total twins 13 658 2 723 4 899 4 273 1 650 186 7 14 409 Single sex 12 534 1 987 3 429 2 851 1 038 124 4 9 979 Different sex 1 124 736 1 470 1 422 612 62 3 4 430 Dizygotes 2 248 1 472 2 940 2 844 1 224 124 6 8 860 Monozygotes 11 410 1 251 1 959 1 429 426 62 1 5 549 Total maternities 2 640 107 236 315 452 421 771 280 466 93 508 13 931 554 1 235 558 Proportion of dizygotes1 0.15 0.38 0.54 0.60 0.67 0.74 0.67 0.86 0.61 Dizygote rate2 0.76 2.31 4.67 6.97 10.14 13.09 8.90 10.83 7.17 Monozygote rate2 4.17 3.82 3.97 4.64 5.10 4.56 4.45 1.81 4.49

20b

Source: ISD (Scotland), SMR021 Proportion based on total number of twins.2 Rates per 1000 maternities.

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Obstetric consequences of multiple pregnancy

Pregnancy complicationsIt is widely reported that rates of all pregnancy complications, major and minor, are increased in multiple pregnancy. However, data from the Aberdeen Maternal and Neonatal Databank suggest that this relationship does not apply to the complication of placenta praevia (Campbell, D.M. personal communication). SMR02 data for 1981 to 2000 were used to examine the rates of selected obstetric complications in singleton and multiple pregnancies. These data are summarised in Tables 21a and 21b.

The data clearly show that multiple pregnancy is associated with increased risks (approximately double) of hypertensive disorder and of postpartum haemorrhage. (Odds ratios compared to singleton pregnancy of 1.99 [95% CI, 1.91-2.08] for hypertensive disorder and of 2.24 [95% CI, 2.12-2.36] for postpartum haemorrhage.) However, in line with the reported Aberdeen finding, and even with these very large numbers, there is no demonstrable increased risk of either placenta praevia or of other categories of antepartum haemorrhage. (Odds ratios compared to singleton pregnancy of 1.23 [95% CI, 0.999-1.50] for placenta praevia and of 1.02 [95% CI, 0.936-1.12] for other antepartum haemorrhage.)

Figure 13b - Rates of mono- and dizygotic twins by maternal age, 1981-2000 (aggregated)


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Numbers hypertensive antepartum placenta postpartum all singleton disorder haemorrhage praevia haemorrhage births 1981 9 168 2 301 383 1 252 67 280 1982 8 885 2 181 323 1 199 64 350 1983 8 778 2 348 373 1 384 63 287 1984 7 917 2 210 348 2 211 63 521 1985 7 847 2 248 370 2 332 64 267

1986 7 701 2 212 403 2 566 63 960 1987 8 356 2 251 353 2 668 64 195 1988 7 605 2 301 356 2 707 64 714 1989 6 721 2 213 319 2 728 62 285 1990 7 072 2 599 338 2 681 63 808

1991 6 669 2 485 329 2 890 65 270 1992 6 673 2 541 335 3 036 63 415 1993 6 597 2 537 342 3 167 61 571 1994 6 511 2 526 323 3 182 59 727 1995 6 313 2 475 344 3 411 58 178

1996 5 441 1 947 352 3 494 56 180 1997 5 084 1 483 301 4 128 57 281 1998 4 271 841 167 4 802 55 441 1999 3 566 800 186 5 171 52 931 2000 3 128 639 138 4 973 49 232

Total 134 303 41 138 6 383 59 982 1 220 893

Rates1

hypertensive antepartum placenta postpartum disorder haemorrhage praevia haemorrhage 1981 136.3 34.2 5.7 18.6 1982 138.1 33.9 5.0 18.6 1983 138.7 37.1 5.9 21.9 1984 124.6 34.8 5.5 34.8 1985 122.1 35.0 5.8 36.3

1986 120.4 34.6 6.3 40.1 1987 130.2 35.1 5.5 41.6 1988 117.5 35.6 5.5 41.8 1989 107.9 35.5 5.1 43.8 1990 110.8 40.7 5.3 42.0

1991 102.2 38.1 5.0 44.3 1992 105.2 40.1 5.3 47.9 1993 107.1 41.2 5.6 51.4 1994 109.0 42.3 5.4 53.3 1995 108.5 42.5 5.9 58.6

1996 96.8 34.7 6.3 62.2 1997 88.8 25.9 5.3 72.1 1998 77.0 15.2 3.0 86.6 1999 67.4 15.1 3.5 97.7 2000 63.5 13.0 2.8 101.0

Total 110.0 33.7 5.2 49.1

21a

1 Rates per 1000 singleton births. Source: ISD (Scotland), SMR02

Codes used in this analysis (please note that due to differences between ICD9 and ICD10 it is not possible to do exact mappings):

ICD9 ICD10Hypertensive disorder 642.- O10.-, O11.X, O13.X, O14.-, O15.-, O16.Antepartum haemorrhage (excluding placenta praevia) 641.2, 641.3, 641.8, 641.9 O45.-, O46.-Placenta praevia 641.0, 641.1 O44.0, O44.1Postpartum haemorrhage 666.- O72.-




Obstetric complications - multiple births, 1981-2000

Numbers hypertensive antepartum placenta postpartum all singleton disorder haemorrhage praevia haemorrhage births 1981 130 22 3 23 602 1982 147 25 5 13 615 1983 161 21 7 13 659 1984 158 24 8 36 684 1985 125 27 2 26 688

1986 170 28 6 43 735 1987 167 25 4 58 726 1988 145 18 2 74 718 1989 136 27 2 58 695 1990 168 26 5 53 754

1991 136 20 3 49 731 1992 173 24 6 85 807 1993 154 38 7 84 783 1994 169 38 5 79 790 1995 159 32 7 112 855

1996 122 35 5 90 788 1997 142 27 5 123 814 1998 135 14 3 164 821 1999 105 17 5 161 725 2000 100 18 4 179 698

Total 2 902 506 94 1 523 14 688

Rates1

hypertensive antepartum placenta postpartum disorder haemorrhage praevia haemorrhage 1981 215.9 36.5 5.0 38.2 1982 239.0 40.7 8.1 21.1 1983 244.3 31.9 10.6 19.7 1984 231.0 35.1 11.7 52.6 1985 181.7 39.2 2.9 37.8

1986 231.3 38.1 8.2 58.5 1987 230.0 34.4 5.5 79.9 1988 201.9 25.1 2.8 103.1 1989 195.7 38.8 2.9 83.5 1990 222.8 34.5 6.6 70.3

1991 186.0 27.4 4.1 67.0 1992 214.4 29.7 7.4 105.3 1993 196.7 48.5 8.9 107.3 1994 213.9 48.1 6.3 100.0 1995 186.0 37.4 8.2 131.0

1996 154.8 44.4 6.3 114.2 1997 174.4 33.2 6.1 151.1 1998 164.4 17.1 3.7 199.8 1999 144.8 23.4 6.9 222.1 2000 143.3 25.8 5.7 256.4

Total 197.6 34.4 6.4 103.7

21b

Codes used in this analysis (please note that due to differences between ICD9 and ICD10 it is not possible to do exact mappings):

ICD9 ICD10Hypertensive disorder 642.- O10.-, O11.X, O13.X, O14.-, O15.-, O16.Antepartum haemorrhage (excluding placenta praevia) 641.2, 641.3, 641.8, 641.9 O45.-, O46.-Placenta praevia 641.0, 641.1 O44.0, O44.1Postpartum haemorrhage 666.- O72.-

1 Rates per 1000 multiple births. Source: ISD (Scotland), SMR02




Figure 15 - Percentage of Caesarean sections (1981-2000)


Mode of deliveryFigure 14 is based on the 20 year aggregated SMR02 data (1981 – 2000) and summarises the modes of delivery for singleton, first twin, and second twin babies during this time period. Overall, 73% of singleton babies had spontaneous vaginal deliveries, compared with 43% of first twins and only 26% of second twins. Twenty two percent of second twins underwent vaginal breech delivery, compared with only four percent of first twins and less than one percent of singletons. There is a discrepancy (354 babies) in the rate of emergency Caesarean section between first and second twin births. Thus, over the 20 year period, the scenario of emergency section for a second twin occurred in 2.5% of all twin deliveries (354/14409).

Figure 15 shows the time trend in rates of elective and emergency Caesarean section for singleton and multiple births (first twin) between 1981 and 2000. The widely recognised upward trend in rates of Caesarean section is confirmed – for both categories of CS and for both singletons and multiples.

Figure 14 - Mode of delivery for singleton, first twin and second twin (1981-2000 aggregated)


20

40

60

80

100emergency CS

elective CS

forceps/ventouse

breech

svd

twin 2twin 1singleton

Per

cant

age

0

5

10

15

20

25

30

35

twin 1emergency cs

singleton elective cs

singleton emergency

twin 1 elective cs

20001999199819971996199519941993199219911990198919881987198619851984198319821981

Per

cent

age




Fetal and infant consequences of multiple birth

MortalityTables 22a and 22b summarise the rates of stillbirth and infant death for singleton and multiple births for the period 1985 to 2000. The overall figures for the 16 year period emphasise the greatly elevated risks of all categories of mortality for multiple, compared to singleton, births. It is widely recognised that preterm birth accounts for much of the increased mortality in multiple births. Tables 23a and 23b summarise stillbirth and infant death data for singleton and multiple births at term. These data show that twin babies have an increased risk of mortality compared with singletons, even when born at term. The excess in mortality for multiples is therefore not entirely attributable to preterm birth.

Stillbirths, neonatal deaths and infant deaths by year, singletons, 1985-2000

Numbers stillbirths neonatal post-neonatal live singleton all singleton deaths deaths births births

1985 330 304 - 65 320 65651 1986 354 263 - 64 368 64725 1987 320 262 - 64 788 65108 1988 336 261 - 64 790 65126 1989 295 238 - 62 102 62398

1990 321 254 - 64 487 64808 1991 327 257 - 65 568 65895 1992 333 264 - 64 153 64486 1993 375 226 - 61 782 62156 1994 360 195 - 60 069 60429

1995 353 183 123 58 372 58725 1996 348 193 124 57 648 57996 1997 290 162 117 57 814 58104 1998 309 158 105 55 674 55983 1999 271 148 87 53 650 53921 2000 278 179 86 51 562 51840

Total1 5 200 3 547 642 972 147 977 351

Rates stillbirths2 neonatal post-neonatal

deaths3 deaths3

1985 5.0 4.6 - 1986 5.5 4.1 - 1987 4.9 4.0 - 1988 5.2 4.0 - 1989 4.7 3.8 -

1990 5.0 3.9 - 1991 5.0 3.9 - 1992 5.2 4.1 - 1993 6.0 3.6 - 1994 6.0 3.2 -

1995 6.0 3.1 2.1 1996 6.0 3.3 2.1 1997 5.0 2.8 2.0 1998 5.5 2.8 1.9 1999 5.0 2.7 1.6 2000 5.4 3.5 1.7

Total1 5.3 3.6 1.9

22a

1 Aggregated totals and rates are based on the 16 years 1985-2000 except for post-neonatal deaths where data are only available for the 6 year period 1995-2000.

2 Rates per 1000 total singleton births.3 Rates per 1000 live singleton births.

Sources: ISD (Scotland), Scottish Stillbirth and Infant Death

Survey and General Register Office (Scotland)




Stillbirths, neonatal deaths and infant deaths by year, multiples, 1985-2000

Numbers stillbirths neonatal post-neonatal live multple all multiple deaths deaths births births 1985 27 49 - 1 364 1 391 1986 27 72 - 1 444 1 472 1987 18 53 - 1 454 1 472 1988 19 40 - 1 424 1 443 1989 21 63 - 1 380 1 401

1990 28 33 - 1 486 1 514 1991 42 34 - 1 456 1 498 1992 23 40 - 1 636 1 659 1993 34 28 - 1 556 1 590 1994 20 50 - 1 588 1 608

1995 44 58 11 1 679 1 723 1996 33 40 8 1 660 1 693 1997 29 27 10 1 626 1 655 1998 42 48 9 1 645 1 687 1999 15 34 7 1 497 1 512 2000 19 33 7 1 514 1 534

Total1 441 702 52 24 409 24 852 Rates stillbirths2 neonatal post-neonatal

deaths3 deaths3

1985 19.4 35.2 - 1986 18.3 48.9 - 1987 12.2 36.0 - 1988 13.2 27.7 - 1989 15.0 45.0 -

1990 18.5 21.8 - 1991 28.2 22.8 - 1992 13.9 24.1 - 1993 21.4 17.6 - 1994 12.4 31.1 -

1995 25.6 33.7 6.4 1996 19.6 23.7 4.7 1997 17.6 16.4 6.1 1998 25.0 28.6 5.4 1999 9.9 22.5 4.6 2000 12.4 21.6 4.6

Total1 17.8 28.3 5.3

22b


2 Rates per 1000 total multiple births.3 Rates per 1000 live multiple births.






Stillbirths, neonatal deaths and infant deaths, singletons born at term (37 weeks and above), 1985-2000

Numbers stillbirths neonatal post-neonatal live singleton all singleton deaths deaths term births term births 1985 129 95 - 60 126 60 263 1986 157 100 - 59 760 59 916 1987 145 82 - 60 122 60 269 1988 132 98 - 60 451 60 583 1989 118 79 - 58 235 58 359

1990 131 82 - 59 452 59 580 1991 150 86 - 61 257 61 409 1992 131 100 - 59 296 59 428 1993 117 82 - 57 733 57 847 1994 118 69 - 55 835 55 962

1995 107 72 86 54 565 54 670 1996 107 66 70 52 618 52 719 1997 78 63 72 53 759 53 832 1998 112 55 62 51 910 52 018 1999 90 41 57 49 456 49 537 2000 87 55 52 46 020 46 093

Total1 1 909 1 225 399 900 595 902 485


deaths3 deaths3

1985 2.14 1.58 - 1986 2.62 1.67 - 1987 2.41 1.36 - 1988 2.18 1.62 - 1989 2.02 1.36 -

1990 2.20 1.38 - 1991 2.44 1.40 - 1992 2.20 1.69 - 1993 2.02 1.42 - 1994 2.11 1.24 -

1995 1.96 1.32 1.58 1996 2.03 1.25 1.33 1997 1.45 1.17 1.34 1998 2.15 1.06 1.19 1999 1.82 0.83 1.15 2000 1.89 1.20 1.13

Total1 2.12 1.36 0.44

23a


2 Rates per 1000 total singleton term births.3 Rates per 1000 live singleton term births.






Stillbirths, neonatal deaths and infant deaths, multiples born at term (37 weeks and above), 1985-2000

Numbers stillbirths neonatal post-neonatal live multiple all multiple deaths deaths term births term births 1985 11 5 - 764 778 1986 4 6 - 796 800 1987 9 2 - 732 741 1988 9 1 - 760 768 1989 3 7 - 725 728

1990 3 5 - 799 803 1991 5 3 - 722 727 1992 3 1 - 763 766 1993 7 0 - 844 851 1994 0 1 - 799 800

1995 4 1 2 829 832 1996 12 0 1 725 734 1997 8 1 1 764 770 1998 8 1 2 797 803 1999 3 1 0 726 726 2000 6 2 2 681 685

Total1 95 37 8 12 226 12 312


deaths3 deaths3

1985 14.14 6.54 - 1986 5.00 7.54 - 1987 12.15 2.73 - 1988 11.72 1.32 - 1989 4.12 9.66 -

1990 3.74 6.26 - 1991 6.88 4.16 - 1992 3.92 1.31 - 1993 8.23 - - 1994 - 1.25 -

1995 4.81 1.21 2.41 1996 16.35 - 1.38 1997 10.39 1.31 1.31 1998 9.96 1.25 2.51 1999 4.13 1.38 - 2000 8.76 2.94 2.94

Total1 7.72 3.03 0.65

23b


2 Rates per 1000 total multiple term births. 3 Rates per 1000 live multiple term births.






Stillbirths and infant deaths with congenital anomalies by year, 1985-2000

Numbers with congenital anomaly without congenital anomaly stillbirths neonatal deaths stillbirths neonatal deaths all births Singletons 511 1 246 4 688 2 301 977 379 Multiples 41 74 400 628 24 812

Rates 1 with congenital anomaly without congenital anomaly stillbirths neonatal deaths stillbirths neonatal deaths Singletons 0.5 1.3 4.8 2.4Multiples 1.7 3.0 16.1 25.3

Preterm birth and low birthweightOur previous publication, Small Babies in Scotland,11 demonstrated the increased rates of both preterm birth and low birthweight for multiple births over the period 1987 to 1996. Table 24 provides similar data updated to 2000.

Preterm and low birthweight babies - singletons and multiples, 1981-2000 (aggregated)

all babies preterm low preterm and birthweight low birthweight

number percentage number percentage number percentage Singleton 1 220 893 70 562 5.8 71 428 5.9 42 198 3.5 Multiple 29 655 14 274 48.1 15 904 53.6 11 464 38.7 Total 1 250 548 84 836 6.8 87 332 7.0 53 662 4.3

24


Congenital anomaliesIt is widely held that multiple births have higher rates of congenital anomaly than singletons, although published prevalence studies give conflicting results.12 Table 25 summarises data on lethal congenital anomalies in singleton and multiple births for the period 1985 to 2000. The extended perinatal mortality (stillbirths plus neonatal deaths) due to congenital anomalies was 1.8 per 1000 births (95% CI, 1.7-1.8) for singletons and 4.6/1000 for multiples (95% CI, 3.8-5.6).

25

1 Rates based on 1000 applicable births.Sources: ISD (Scotland), Scottish

Stillbirth and Infant Death Survey and General

Register Office (Scotland)




Neonatal unit service utilisationCurrently, around one in seventy births is a multiple birth. However, these births require a disproportionate amount of health service resource utilisation. Table 26a summarises recent data (1996-2000) on neonatal unit admissions of singleton and multiple newborns. Over the five-year period, admission to a neonatal unit for >48 hours occurred in only around six percent of singleton babies, but in 38% of twins and in 88% of higher order multiple births.

Among those babies who are admitted to a neonatal unit, the average length of stay (1997-2000) was three days for singletons, seven days for twins and 18 days for higher order multiples. Using these data, total neonatal unit utilisation over the five year period, 1996-2000, has been calculated and summarised in Table 26b. Multiple births account for only 2.8% of all births, but for a quarter of neonatal unit occupancy.

Babies admitted to NNU for >48hrs for singletons, twins and other multiples by year, 1996-2000

ingletons not <=48hrs >48hrs Not known Total % admitted admitted known >48hrs 1996 50 070 2 511 3 412 187 55 993 6.1 1997 50 881 2 531 3 599 270 57 011 6.3 1998 49 411 2 271 3 451 308 55 133 6.3 1999 47 022 2 265 3 392 252 52 679 6.4 2000 43 711 2 137 3 131 253 48 979 6.4 Total 241 095 11 715 16 985 1 270 269 795 6.3 Twins not ≤48hrs >48hrs Not known Total % admitted admitted known >48hrs 1996 761 142 598 21 1 501 39.8 1997 827 144 598 21 1 569 38.1 1998 835 150 577 44 1 562 36.9 1999 735 130 551 12 1 416 38.9 2000 690 136 517 15 1 343 38.5 Total 3 848 702 2 841 113 7 391 38.4 Triplets+ not ≤48hrs >48hrs Not known Total % admitted admitted known >48hrs 1996 3 2 47 29 52 90.4 1997 4 1 45 7 50 90.0 1998 11 1 41 1 53 77.4 1999 3 - 29 1 32 90.6 2000 4 - 53 - 57 93.0 Total 25 4 215 38 244 88.1

26a

Neonatal unit occupancy by singletons and multiples 1996-2000 (babies for which neonatal unit admission status was recorded)

Singleton Twin Triplet+ Total

Number of babies 269 795 7 391 244 277 430 % of all babies 97.2 2.7 0.1 100 Number admitted 28 700 3 543 219 32 462

Average stay of those admitted (days) 3 7 18 Total cot-days 86 100 24 801 3 942 114 843 % of all cot-days 75.0 21.6 3.4 100

26b






Chapter references

1 Cole SK, Hey EN, Thomson AM. Classifying perinatal death: an obstetric approach. Brit J Obstet Gynaecol 1986;93:1204-12.

2 Hey EN, Lloyd DL, Wigglesworth JS. Classifying perinatal death: fetal and neonatal factors. Brit J Obstet Gynaecol 1986;93:1213-23.

3 Cole S, Hartford RB, Bergsjo P, McCarthy B. International Collaborative Effort (ICE) on birthweight, plurality, perinatal and infant mortality. (iii: a method of grouping underlying causes of infant death to aid international comparisons) Acta Obstet Gynecol Scand 1989, 68: 113-117.

4 FIGO. Standing committee on perinatal mortality and morbidity. Report of committee following a workshop on monitoring and reporting perinatal mortality and morbidity. Chameleon Press Ltd, London, 1982, p12.

5 Wigglesworth JS. Monitoring perinatal mortality. Lancet 1980;2:684-6.

6 Twinning and twins. MacGillivray I, Campbell DM, Thompson B, eds. Chichester: John Wiley & Sons, 1988.

7 Macfarlane A, Mugford M. Birth Counts: statistics of pregnancy and childbirth. Norwich: The Sta-tionery Office, 2000.

8 Duncan JM. On the comparative frequency of twin-bearing in different pregnancies. Edinburgh Medi-cal Journal 1865;10:928-9.

9 Tchouriloff M. Bulletin de la Societe d’Anthropologie de Paris 2002;12:440-6.

10 Carstairs V, Morris R. Deprivation and health in Scotland 1993. Aberdeen Univ. Press, 1993.

11 ISD Scotland. Small Babies in Scotland: a ten year overview 1987-1996. Births in Scotland Publication Series 2, 1-39. 1998.

12 Little J, Bryan EM. Congenital anomalies. In MacGillivray I, Campbell DM, Thompson B, eds. Twin-ning and twins, pp 207-40. John Wiley & Sons Ltd, 1988.

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