Neonatal and Early Childhood Outcomes of Preterm Twin and Singleton Infants.

OBJECTIVE: Whether preterm twin infants are at a greater risk of neonatal and neurodevelopmental outcomes than preterm singleton infants is currently unclear. This information is relevant for parental counseling in pregnancies at risk of extreme preterm birth. We aimed to compare neonatal and early-childhood outcomes of preterm twins and preterm singletons and explore the association of chorionicity with outcomes.

STUDY DESIGN: This was a national retrospective cohort study of singleton and twin infants admitted at 230/7 -286/7 weeks to level-III NICU's in Canada (2010-2020). The primary neonatal outcome was a composite of neonatal death or severe neonatal morbidities. The primary early-childhood outcome was a composite of death or significant neurodevelopmental impairment (sNDI).

RESULTS: The study cohort included 3,554 twin and 12,815 singleton infants. Twin infants born at 230/7 -256/7 weeks had a higher risk of the composite neonatal outcome (aRR 1.04, 95%-CI 1.01-1.07). However, these differences were limited to the subgroups of same-sex and monochorionic twin pregnancies. Twin infants of 230/7 -256/7 weeks were also at an increased risk of the composite early-childhood outcome (aRR 1.22, 95%-CI 1.09-1.37). Twin infants of 260/7 -286/7 weeks were not at an increased risk of adverse neonatal outcomes or the composite early-childhood outcome compared with singleton infants.

CONCLUSIONS: Among infants born at 230/7 -256/7 weeks, twins have a higher risk of adverse neonatal outcomes and the composite early-childhood outcome than singleton infants. However, the increased risk of adverse neonatal outcomes is mostly limited to monochorionic twins and may thus be driven by complications related to monochorionic placentation.