Intertwin birth weight discordance, mode of delivery, and fetal and neonatal outcomes in twin pregnancies

OBJECTIVE: The aim of the present study was to evaluate the association between intertwin birth weight discordance and fetal and neonatal outcomes in twin pregnancies, and to assess its relationship with mode of delivery. METHODS: This retrospective cohort study included twin pregnancies delivered at a tertiary referral center. Intertwin birth weight discordance was calculated as the percentage difference between the larger and smaller twin and categorized as 0%-15%, 15%-25%, and >25%. Fetal and neonatal outcomes were analyzed as predefined composite outcomes. Multivariable logistic regression models were used to assess associations, adjusting for gestational age at delivery, antenatal corticosteroid exposure, chorionicity, and mode of delivery. RESULTS: A total of 1408 twin pregnancies (2816 newborns) were included. In bivariate analyses, higher intertwin birth weight discordance was associated with increased rates of adverse fetal and neonatal outcomes. However, after adjustment, birth weight discordance was not significantly associated with the fetal composite outcome (discordance >25%: odds ratio [OR] 2.55; 95% confidence interval [CI]: 0.89-7.27), although the magnitude of the effect suggested a possible increased risk, nor the neonatal composite outcome (OR 1.53; 95% CI: 0.97-2.40). Gestational age at delivery was inversely associated with both fetal (OR 0.75 per week; 95% CI: 0.66-0.84) and neonatal composite outcomes (OR 0.54 per week; 95% CI: 0.45-0.65). Cesarean delivery (OR 2.26; 95% CI: 1.58-3.25) and antenatal corticosteroid exposure (OR 1.75; 95% CI: 0.99-3.08) were associated with increased odds of neonatal composite morbidity. CONCLUSION: Intertwin birth weight discordance was not independently associated with adverse fetal or neonatal outcomes after adjustment. Prematurity emerged as the main determinant of perinatal risk, supporting interpretation of birth weight discordance as a contextual marker rather than an independent determinant of delivery strategy or timing.