RESUMO
OBJECTIVE: The purpose of this study was to determine the perinatal outcome in monoamniotic twin pregnancies and to review the recently published literature about the topic. METHODS: This retrospective study examined the records of prenatally diagnosed monoamniotic twin pregnancy casese in our institution between January 1997 and April 2010. RESULTS: Among 1,112 twin pregnancies, there were 15 (1.3%) monoamnionic twins, including 2 conjoined twin pregnancies. Twelve (80%), 9 (60%), 5 (33.3%), and 4 pregnancies (26.7%) delivered after 20, 30, 32, and 34 weeks, respectively. Among 12 pregnancies that continued after 20 weeks of gestation, three cases showed one-fetal death and one, both-fetal death. The perinatal mortality rate (from 20 weeks of gestation to 28 days after birth) was 37.5%. The incidence of lethal anomalies and congenital heart anomalies was 20% and 23.3%, respectively. The mean gestational age at delivery was 31.4+/-4.53 weeks; 16 of 18 neonates (84.2%) were admitted to the neonatal intensive care unit (NICU). Three neonates expired on the first day after birth. The mean duration of the NICU stays for 13 live neonates was 32.0+/-29.3 days (range, 3 to 114 days). The main causes of perinatal deaths were preterm birth, congenital anomalies, pregnancy loss before 20 weeks, and intrauterine fetal demise that might have resulted form cord entanglement. CONCLUSION: Perinatal mortality in monoamniotic twins was still very high and the survival rate after 32 weeks of gestation is approximately one-third. Further studies are needed to improve the perinatal mortality.