Term perinatal mortality and morbidity in monochorionic and dichorionic twin pregnancies: A retrospective study

Aim. Perinatal mortality and morbidity in monochorionic (MC) twins appears to be increasing compared to dichorionic (DC) twins. The aim of our study was to determine the difference in perinatal mortality and morbidity in MC and DC twins born after 37 weeks' gestation. Design. A retrospective, cross-sectional study of medical records. Setting. Large tertiary care centre in the Netherlands. Population. All twins delivered >= 37 gestational weeks at the Leiden University Medical Centre between 1988 and 2004 were included in the study. Methods. Perinatal outcome was assessed in all term twins. Differentiation between a MC study group and a DC control group was made based on gender, intertwin membrane histology, or first trimester ultrasound. Main outcome measures. Perinatal mortality and morbidity was assessed. Morbidity was defined as admission to the neonatal nursery. Results. We included 383 DC and 74 MC twin pregnancies. Three fetuses died in utero in two MC pregnancies at 38 gestational weeks. One surviving MC co-twin had a right-sided hemiparesis due to a large parenchymal defect in the left cerebral hemisphere. Perinatal mortality was 2% (3/148) in MC and 0% (0/766) in DC twins (p=0.004). The admission rate to the neonatal nursery was 27% in MC and 19% in DC twins (p=0.031). Conclusions. At term, MC twins have a higher risk for perinatal mortality and a higher admission rate to the neonatal nursery compared to DC twins. Given the increased mortality, a prospective study is needed to determine the effects of elective delivery in uncomplicated MC twin pregnancies at around 37 weeks' gestation.