UOG Journal Club: May 2012
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Transcript of UOG Journal Club: May 2012
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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)
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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
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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)
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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
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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
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SOUTHWEST THAMES OBSTETRIC RESEARCH COLLABORATIVE (STORK)SOUTHWEST THAMES OBSTETRIC RESEARCH COLLABORATIVE (STORK)
Nine UK hospitals, 16 collaboratorsNine UK hospitals, 16 collaborators
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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
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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
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Gestational age (weeks)
Bir
th (
%)
Monochorionic
Dichorionic
Timing of birth in twin pregnancy
Modal time of deliveryMC = 36–37 weeksDC = 37–38 weeks
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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
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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
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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
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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
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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
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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