Perinatal mortality and morbidity, timing and route of delivery in monoamniotic twin pregnancies: a retrospective cohort study.

Purpose: Monoamniotic twin pregnancies are at high risk of perinatal complications and fetal loss. The objective of this study is to describe the management and outcomes of monoamniotic twin pregnancies in a French university obstetrics department.
Methods: Retrospective review of all consecutive monoamniotic twin pregnancies managed between 1992 and 2018 in a level-3 university hospital maternity unit. Antenatal variables, gestational age and other neonatal characteristics at delivery, mode of delivery, and its reason were recorded, together with outcomes, including a composite adverse neonatal outcome.
Results: Overall, 46 monoamniotic twin pregnancies (92 fetuses) were identified during the study period. Among them, 27 fetal losses and 2 early neonatal deaths were reported. Congenital abnormalities accounted for 33.3% of the 27 fetal losses, and unexpected fetal deaths for 29.6%. Among the 37 women who gave birth to 65 live infants at 23 or more weeks of gestation, 17 had cesarean and 19 vaginal deliveries. Overall and composite adverse neonatal outcomes did not differ significantly for the 33 children born vaginally and the 31 by cesarean deliveries. The prospective risk of intrauterine death in all 92 fetuses reached its nadir of 1.8% at 33 ^6/7  weeks.
Conclusion: This series confirms the still high risk of fetal and neonatal death of these twins and shows that congenital abnormalities but also unexpected fetal deaths account for the majority of pre- and postnatal mortality. Our data suggest that vaginal delivery of monoamniotic twins is safe and that delivery for uncomplicated monoamniotic twins should be considered around 33 weeks of gestation, but not later than 35 weeks.