Objective: This study aimed to evaluate the perinatal outcome of twin pregnancies delivered in a tertiary teaching hospital according to chorionicity.
Methods: A retrospective study involving 289 twin pregnancies delivered from January 2003 to December 2006 was carried out. Maternal and perinatal data were obtained from hospital charts and delivery logs. Chorionicity was determined by ultrasonography or histopathological study.
Results: Incidence of twin gestations was 3.4% and 96.4% were spontaneously conceived. 60.5% were dichorionic (DC), 30.8% of monochorionic diamniotic (MCDA), 6.6% monochorionic monoamniotic (MCMA) and for 2.1% chorionicity was unknown. The mean gestation age at delivery was respectively 35.4, 33.6, 32.9 for DC, MCDA and MCMA. The mean birth weight was 2.171, 1.832 and 1.760 g respectively for DC, MC and MCMA. The proportion of fetuses delivered with less than 34 weeks in DC was of 21.7%, while in MCDA it was of 39.3% and in MCMA of 42.1%. Birth weight below the 10th centile occurred in 15.7% for DC, 22.5% for MCDA and 26.3% in MCMA. Congenital anomalies were observed in 21.3% in monochorionic and in 7.4% in the dichorionic. Length of hospital stay was shorter for DC when compared to MCDA and MCMA twins (13.1, 17.3 and 23.3 days, respectively). The proportion of twin pregnancies with both babies discharged alive were 85.7% in DC and 61.1% in MC.
Conclusion: The rate of preterm deliveries and low birth weight is higher in monochorionic pregnancies when compared to dichorionic twins. However, when adjusted for complications such as fetal abnormalities and twin-twin transfusion syndrome, double survival rates were similar in the two groups.