This Journal Club presentation provides a summary and discussion of the following free access article published in UOG: Prospective risk of late stillbirth in monochorionic twins: A regional cohort study Southwest Thames Obstetric Research Collaborative (STORK) Volume 39, Issue 5, Date: May 2012, pages 500-504 This can be accessed here: http://onlinelibrary.wiley.com/doi/10.1002/uog.11110/abstract

1. UOG Journal Club: May 2012
Prospective risk of late stillbirth in monochorionic twins:
a regional cohort study
Southwest 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)

2. Stillbirth rate in twin pregnancy
Current evidence
10 Large numbers (n = 35 647)
9 But no data on chorionicity
Stillbirth rate per 1000
8
7
fetuses at risk
6
5
4
3 Twins
2 Singleton
1
0
28 30 32 34 36 38 40 42
Gestational age (weeks)
Joseph K et al., BMC Pregnancy Childbirth 2003

3. Cumulative perinatal loss rate in twins
Current evidence
Monochorionic
Chorionicity data
But small numbers (n = 467)
Cumulative loss rate (%)
Fetal loss: MC DC
Pregnancies (%) 12.7 2.5*
Fetuses (%) 12.2 1.8*
Perinatal loss:
Dichorionic Pregnancies (%) 4.9 2.8
Fetuses (%) 2.8 1.6
Gestation (weeks) * P < 0.05
Sebire NJ et al., BJOG 1997

4. 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 regional
cohort of twin pregnancies of known chorionicity
Retrospective data;
3005 twin pregnancies
delivered after 26 weeks
from 2000 to 2009

5. Methodology
Inclusion criteria Exclusion criteria
1) Confirmed diamniotic twin 1) Unknown chorionicity
pregnancy at 11 weeks 2) Delivery < 26 weeks
2) 9 hospitals in the Southwest Thames 3) TOP
region of England 4) Stillbirth with a birth weight of < 500g
3) 2000-2009
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

6. SOUTHWEST THAMES OBSTETRIC RESEARCH COLLABORATIVE (STORK)
Nine UK hospitals, 16 collaborators

7. Pregnancy management
11–14 weeks Delivery
•GA according to the CRL • Mode according to patient’s
•Chorionicity (lambda/T-signs) decision and local clinical practice
20–22 weeks • Routine IOL ≥ 38 weeks
•Routine anomaly scan • Elective CS ≥ 36 weeks for MC
and ≥ 37 weeks for DC twins
3rd trimester
•Ultrasound every 3–5 weeks Analysis
•Scans more frequently
• SB risk: derived for each 2-week
as clinically indicated GA interval from 26 weeks
•MC twins had additional scans at
• SB risk expressed per fetus
17 and 19 weeks (for TTTS)

8. Results
MC pregnancies DC pregnancies
Live births
(n = 528) (n = 2424)
GA at delivery (weeks) 36 (34–37) 37 (35–38)*
Birth weight centile 18.4 (4.0–44.8) 22.9 (6.2–50.7)*
Stillbirths MC pregnancies DC pregnancies
(n = 21) (n = 32)
GA at death (weeks) 32 (31–34) 34 (32–36)
Birth weight centile 3.9 (0.2–28.3) 1.1 (0.1–10.0)
* P < 0.05

9. Timing of birth in twin pregnancy
Modal time of delivery
MC = 36–37 weeks
DC = 37–38 weeks
Birth (%)
Monochorionic
Dichorionic
Gestational age (weeks)

10. Late stillbirth risk in twin pregnancy
9
8
1000 ongoing fetuses
7 Monochorionic
Stillbirth risk per
6
5
4
3
Dichorionic
2
1
0
26 28 30 32 34 ≥ 36
Gestational age (weeks)
SB risk in MC twins did not change significantly between 26 and 36 weeks (OR = 1.85 (0.3–13.2))

11. Late stillbirth risk in twin pregnancy
Risk of stillbirth compared to 26+0–27+6 weeks
Monochorionic Dichorionic
>36 >36
Gestational age
Gestational age
34-36 34-36
(weeks)
(weeks)
32-34 32-34
30-32 30-32
28-30 28-30
0.1 1 10 0.1 1 10
Odds ratio Odds ratio
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)

12. Strengths
Current study Previous studies
•Management according to a • Smaller numbers
protocol consistent with current
clinical practice • No standardized protocol for fetal
•Modal time of delivery for MC surveillance
and DC twins of 36 and 37 wk
• Elective delivery of many MC twins
•Largest twin cohort to provide
data on chorionicity-related risk of before 37 weeks
late SB
Limitations
• Retrospective design (validation of the ultrasound database against delivery suite
and national SB registers)
• Assumptions made about GA at which IUD was diagnosed

13. Stillbirth versus prematurity
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

14. Prospective risk of late stillbirth in MC twins
STORK, UOG 2012
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

15. Prospective risk of late stillbirth in MC twins
STORK, UOG 2012
Discussion points
• 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?