Neonatal morbidity and mortality among growth-discordant dichorionic twins, classified according to birth weight of the smaller twin: a population-based cohort study.

Objective:To examine the outcomes among discordant dichorionic (DC) twins, where the smaller twin is small for gestational age (SGA) or non-SGA. Materials and methods:We used the national perinatal registry to compare the relationship between selected maternal characteristics (age, parity, body mass index, gestational diabetes, hypertensive disorders, and gestational age at delivery) and neonatal outcomes in discordant >25% DC twins. Chorionicity was established by standard ultrasound criteria and confirmed postpartum. The smaller of the twins was further classified as SGA or non-SGA. The neonatal outcomes included 5-min Apgar score <7, admission to neonatal intensive care unit, early neonatal death and neonatal morbidities. Results:We identified 377 pairs of DC discordant twins >25% born during the 15 years study period, 270 (71.6%) of which included an SGA smaller twin and 107 (28.4%) were non-SGA smaller twin. Maternal characteristics and neonatal morbidities were unrelated to the smaller discordant twin being SGA. A significantly increased incidence of stillbirth was found in the SGA group. Early neonatal deaths were only found in the SGA group. Conclusion:When the smaller twin is SGA, the growth discordant DC twin pair is associated with increased incidence of perinatal deaths. These appear unrelated to maternal characteristics and neonatal morbidity.