Impact of head-to-abdominal circumference asymmetry on outcomes in growth-discordant twins

OBJECTIVE: Our aim was to evaluate head-to-abdominal circumference asymmetry as a marker for adverse outcomes in growth-discordant twins. STUDY DESIGN: We conducted a retrospective cohort study of asymmetric and symmetric twins with ≥25% growth discordance, comparing their outcomes with those in concordant symmetric twins. Growth was termed asymmetric on the basis of a head circumference/abdominal circumference ratio at ≥95th percentile on ultrasonography performed ≤4 weeks before delivery. RESULTS: We evaluated 572 twin pairs. Asymmetric discordant twins were more likely than symmetric concordant twins to be delivered at ≤34 weeks' gestation (57% vs 27%), to require intubation (36% vs 7%), to remain in intensive care > 1 week (36% vs 3%), and to have an outcome composite that included respiratory morbidity, intraventricular hemorrhage, sepsis, or neonatal death (29% vs 6%), all P < .05. Symmetric discordant and symmetric concordant twins had similar outcomes. CONCLUSIONS: Discordant twins with head-to-abdominal circumference asymmetry have an increased risk of morbidity. Moreover, in the absence of asymmetry, outcomes are comparable among discordant and concordant twins.