Management of monoamniotic twin pregnancies: a case series and systematic review of the literature.
To review the experience of the University of Toronto Perinatal Complex, Ontario, Canada concerning antenatally diagnosed monoamniotic twin pregnancies; and to compare our results with cases reported in the literature with respect to antenatal surveillance and perinatal outcome. A retrospective chart review of all twin gestations from 1993 to April 2000 was performed. A systematic review of the literature, 1966 to April 2000, of perinatal outcome in monoamniotic twin pregnancies was undertaken. All monoamniotic twin gestations at the University of Toronto. Case-series: 25 prenatally diagnosed monoamniotic twin pregnancies were identified. Seven pregnancies were affected by fetal anomalies. One fetus died at 29 weeks. Neonatal complications occurred below 33 weeks of gestational age and were related to immaturity. Systematic review of the literature: 49 studies met our selection criteria and reported 88 cases diagnosed antenatally. Fourteen pregnancies were affected by major congenital anomalies. Twenty fetuses died after 24 weeks of gestation. Neonatal complications varied widely in severity and depended on gestational age at birth. The risk of intrauterine fetal death was 10% at the University of Toronto and 12% in the review of the literature. Our experience, the largest so far, suggests that regular fetal surveillance and appropriate steroid administration leads to a good perinatal outcome. The risk of fetal death (10%-12%) is lower than the previously quoted risk of 30%-70%. A careful review of obstetric interventions and further work examining outpatient surveillance of monoamniotic twin pregnancies are needed. The best treatment of monoamniotic twin pregnancies can only be determined by randomised trials.