Perinatal mortality and morbidity in twin pregnancies: the relation between chorionicity and gestational age at birth

To investigate perinatal mortality and morbidity rates of twin pregnancies and to determine the underlying factors responsible for the increase in these rates.

Records of 300 twin pregnancies which have been followed in our clinic between 1996 and 2005 were reviewed retrospectively. Perinatal mortality and morbidity rates, zygocity, chorionicity, gestational age at delivery, route of conception, birth weight, route of delivery, fetal gender and cesarean rates were investigated.

A total of 16,549 deliveries have been reviewed and 2.9% (n = 484) of these were detected to be twin deliveries. Perinatal mortality, adjusted perinatal mortality, fetal loss, neonatal mortality and perinatal morbidity rates were 7.5, 6.9, 3, 5.8 and 15.4%, respectively. The principal causes of perinatal mortality were prematurity, fetal demise and congenital abnormalities. The main cause of morbidity was respiratory distress syndrome (RDS). In neonatal period 28% of newborns needed neonatal intensive care unit (NICU) and 12.1% received positive pressured ventilation (PPV). Perinatal mortality and morbidity rates were found to be independent from zygocity, instead they were closely linked with chorionicity. Perinatal mortality and morbidity were higher if maternal age was under 18 and over 35, and were not effected by intrauterine growth retardation (IUGR), discordance between twins or RDS prophylaxis.

Twin pregnancies have higher perinatal mortality and morbidity rates and potential obstetrical complications compared to singleton pregnancies, therefore should be monitored more intensely, appropriate precautions should be taken against obstetrical complications, especially before 31-32 weeks of gestation, deliveries should be performed in referral centers with competent NICUs.