UOG Journal Club: May 2012Prospective risk of late stillbirth in monochorionic twins:
a regional cohort studySouthwest Thames Obstetric Research Collaborative (STORK)
Volume 39, Issue 5, Date: May 2012, pages 500–504
Journal Club slides prepared by Dr Asma Khalil(UOG Editor for Trainees)
Stillbirth rate in twin pregnancyCurrent evidence
Joseph K et al., BMC Pregnancy Childbirth 2003
0
1
2
3
4
5
6
7
8
9
10
28 30 32 34 36 38 40 42
Gestational age (weeks)
Sti
llb
irth
rat
e p
er 1
000
fetu
ses
at r
isk
TwinsSingleton
Large numbers (n = 35 647)But no data on chorionicity
Sebire NJ et al., BJOG 1997
Cu
mu
lati
ve l
oss
rat
e (%
)
Gestation (weeks)
Monochorionic
Dichorionic
Cumulative perinatal loss rate in twinsCurrent evidence
Fetuses (%) 12.2 1.8*
2.5*Pregnancies (%) 12.7
Fetal loss: DCMC
Fetuses (%) 2.8 1.6
2.8Pregnancies (%) 4.9
Perinatal loss:
* P < 0.05
Chorionicity dataBut small numbers (n = 467)
Prospective risk of late stillbirth in monochorionic twins: a regional cohort study
STORK, UOG 2012
Objective
Evaluate the prospective risk of late stillbirth in a large regionalcohort of twin pregnancies of known chorionicity
Retrospective data;3005 twin pregnanciesdelivered after 26 weeksfrom 2000 to 2009
Methodology
Inclusion criteria
1) Confirmed diamniotic twin pregnancy at 11 weeks
2) 9 hospitals in the Southwest Thames region of England
3) 2000-2009
Exclusion criteria
1) Unknown chorionicity 2) Delivery < 26 weeks3) TOP 4) Stillbirth with a birth weight of < 500g
Data sources
•Scan data: computerized search of each hospital’s obstetric ultrasound computer database of all twins at 11–14-week nuchal scan•Stillbirth data: Centre for Maternal and Child Enquiries (CMACE)
Mandatory national register of all stillbirths GA at IUD and delivery
•Computerized maternity records were cross-linked to stillbirth data
SOUTHWEST THAMES OBSTETRIC RESEARCH COLLABORATIVE (STORK)SOUTHWEST THAMES OBSTETRIC RESEARCH COLLABORATIVE (STORK)
Nine UK hospitals, 16 collaboratorsNine UK hospitals, 16 collaborators
Pregnancy management
11–14 weeks
•GA according to the CRL
•Chorionicity (lambda/T-signs)
20–22 weeks
•Routine anomaly scan
3rd trimester
•Ultrasound every 3–5 weeks
•Scans more frequently as clinically indicated
•MC twins had additional scans at 17 and 19 weeks (for TTTS)
Delivery
• Mode according to patient’s decision and local clinical practice • Routine IOL ≥ 38 weeks
• Elective CS ≥ 36 weeks for MC and ≥ 37 weeks for DC twins
Analysis
• SB risk: derived for each 2-week GA interval from 26 weeks
• SB risk expressed per fetus
Results
Birth weight centile 18.4 (4.0–44.8) 22.9 (6.2–50.7)*
37 (35–38)*GA at delivery (weeks) 36 (34–37)
Stillbirths
Live births DC pregnancies (n = 2424)
MC pregnancies (n = 528)
DC pregnancies (n = 32)
MC pregnancies (n = 21)
Birth weight centile 3.9 (0.2–28.3) 1.1 (0.1–10.0)
34 (32–36)GA at death (weeks) 32 (31–34)
* P < 0.05
Gestational age (weeks)
Bir
th (
%)
Monochorionic
Dichorionic
Timing of birth in twin pregnancy
Modal time of deliveryMC = 36–37 weeksDC = 37–38 weeks
Late stillbirth risk in twin pregnancy
SB risk in MC twins did not change significantly between 26 and 36 weeks (OR = 1.85 (0.3–13.2))
0
1
2
3
4
5
6
7
8
9
26 28 30 32 34 ≥ 36
Sti
llbir
th r
isk
per
10
00 o
ng
oin
g f
etu
ses
Gestational age (weeks)
Monochorionic
Dichorionic
Late stillbirth risk in twin pregnancy Risk of stillbirth compared to 26+0–27+6 weeks
Total stillbirth rate: MC twins = 19.1 (12.5–29.1) fetuses/1000 ongoing fetuses DC twins = 6.5 (4.6–9.2) ) fetuses/1000 ongoing fetuses OR = 2.97 (95% CI 1.7–5.28)
0.1 1 10
28-30
30-32
32-34
34-36
>36
Odds ratio
Monochorionic
Ges
tati
on
al a
ge
(wee
ks)
0.1 1 10
28-30
30-32
32-34
34-36
>36
Odds ratioG
esta
tio
nal
ag
e (w
eeks
)
Dichorionic
Strengths
Current study
•Management according to a protocol consistent with current clinical practice•Modal time of delivery for MC and DC twins of 36 and 37 wk•Largest twin cohort to provide data on chorionicity-related risk of late SB
Previous studies
• Smaller numbers
• No standardized protocol for fetal surveillance
• Elective delivery of many MC twins before 37 weeks
• Retrospective design (validation of the ultrasound database against delivery suite and national SB registers)• Assumptions made about GA at which IUD was diagnosed
Limitations
Stillbirth risk
Total stillbirth rate >26 weeks approaches 2% in MC twins
Late preterm delivery
1) Infant death rate >32 weeks is 1%
2) Respiratory distress syndrome at 32 weeks 5%
3) Cerebral palsy is 3 x higher at 34 weeks than at term
Stillbirth versus prematurity
Conclusion The risk of SB in MC twins does not appear to increase significantly near term
The data do not support a policy of elective delivery at less than 36 weeks in uncomplicated MC twins
Prospective risk of late stillbirth in MC twins STORK, UOG 2012
Prospective risk of late stillbirth in MC twins STORK, UOG 2012
• What is your local hospital policy for timing of delivery of MC and DC twins?
• Is the clinical evidence for your local policy robust?
• How did the researchers capture all twin pregnancies in this cohort?
• How did the researchers capture all the stillbirths from this cohort?
• Was the stillbirth risk in MC different from that of DC twins?
• Did the stillbirth risk in MC twins increase significantly at any gestational age?
• Do the risks of continuing MC pregnancy beyond 34 weeks’ gestation outweigh the risks of preterm delivery?
Discussion points
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