Monoamniotic twins in contemporary practice: a single-center study of perinatal outcomes

Objective. The previous studies of monochorionic monoamniotic (MCMA) twins reported perinatal mortality rates as high as 70-80%. The recent trends have been towards significantly improved outcomes, though results from all studies have not been consistent. Method. A retrospective cohort analysis of all MCMA pregnancies >= 20 weeks delivered in a single university institution from 2001 to 2009, using a computerised hospital database. MCMA twins are managed by a close antenatal surveillance program, preferably elective admission at 26-28 weeks, daily non-stress tests, regular assessment of fetal growth with the goal of cesarean delivery by 34 weeks. Results. Of the 25 MCMA pregnancies delivered, 98% (49/50) of twins were live-born. All women were delivered by cesarean section. There was one intrauterine fetal demise, which was secondary to anencephaly. There were three neonatal deaths, two in association with complex congenital heart disease. One twin died outside the neonatal period following cardiac surgery. In total, 28% (7/25) of pregnancies were complicated by major congenital anomalies. There was one case of mild transient twin-twin transfusion syndrome (TTTS). The overall perinatal mortality rate for non-anomalous twins was 2.4% (95% CI = 0.06%-13.59%). Conclusions. Traditionally quoted as up to 80%, perinatal mortality rates <10% for MCMA twins are achievable in contemporary practice. It is vital that these high-risk pregnancies are managed in experienced centers with close surveillance and appropriate pediatric support.