Preterm discordant twins: What birth weight difference is significant?

Abstract

Objective: The purpose of this study was to determine the effect of discordant fetal growth on subsequent perinatal and neonatal outcome for different degrees of birth weight discordance in preterm twin gestations. Study design: One hundred twenty-two live born twin sets delivered between 25 and 34 completed weeks' gestation were retrospectively studied. They were stratified into five categories according to the percent difference in infant birth weight: < 10%, 10% to 15%, 15% to 20%, 20% to 30%, and > 30%, which was defined as ([Birth weight of larger twin - Birth weight of smaller twin]/Birth weight of larger twin) x 100. The relationship between different birth weight categories and the perinatal and neonatal outcome and the difference in outcome between the large and small infants within each category were determined. Results: Preterm twin gestations with > 30% birth weight discordance were associated with a higher incidence of infant death (25%), congenital anomalies (37.5%), small-for-gestational-age infants (31.8%), Apgar score < 7 at 5 minutes (33.3%), and periventricular leukomalacia (16.7%), in spite of a higher cesarean delivery rate (79.2%). Outcomes of large and small infants within categories were similar except in the > 30% group, where all deaths occurred in the small infants. Conclusion: In preterm twin gestations the use of a 30% birth weight difference to define twin discordance is most clinically relevant in identifying those infants at risk for adverse perinatal outcome.