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UOG Journal Club: May 2012

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

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UOG Journal Club: May 2012

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  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) But no data on chorionicity 9 8 7 6 Stillbirth rate per 1000fetuses at risk 5 4 Twins 3 Singleton 2 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) MC DC Fetal loss: Cumulative loss rate (%) Pregnancies (%) 12.7 2.5* Fetuses (%) 12.2 1.8* Perinatal loss: Dichorionic Pregnancies (%) 4.9 2.8 2.8 1.6 Fetuses (%) 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 • Confirmed diamniotic twin pregnancy at 11 weeks • 9 hospitals in the Southwest Thames region of England • 2000-2009 • Exclusion criteria • Unknown chorionicity • Delivery < 26 weeks • TOP • 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

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

  7. 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

  8. Results MC pregnancies (n = 528) DC pregnancies (n = 2424) Live births 36 (34–37) 37 (35–38)* GA at delivery (weeks) Birth weight centile 18.4 (4.0–44.8) 22.9 (6.2–50.7)* MC pregnancies (n = 21) DC pregnancies (n = 32) Stillbirths 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 Monochorionic Birth (%) Dichorionic Gestational age (weeks)

  10. Late stillbirth risk in twin pregnancy 9 8 Monochorionic 7 6 Stillbirth risk per 1000 ongoing fetuses 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 34-36 34-36 Gestational age (weeks) Gestational age (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 • 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 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 • Infant death rate >32 weeks is 1% • Respiratory distress syndrome at 32 weeks 5% • 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?

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