Gestational age and antenatal growth discordance are principal predictors of composite neonatal outcomes in very preterm twins

Abstract Very preterm twin pregnancies show heterogeneous neonatal trajectories that are incompletely captured by infant-level survival alone. Pregnancy-level neonatal outcomes and their antenatal and perinatal determinants were evaluated in 434 dichorionic and monochorionic twin pregnancies managed at a national tertiary referral center between 2013 and 2024. The primary outcome was composite survival without major neonatal morbidity (C-SNM). Secondary outcomes were composite morbidity burden (CoMB; neither twin, one twin, or both twins affected), cumulative morbidity burden (CMB; the unweighted number of affected clinical domains across both infants), and dominant organ-system morbidity (DSM; organ system contributing most to morbidity). C-SNM was achieved in 222/434 pregnancies (51.2%). In multivariable analyses, gestational age at delivery and antenatal estimated fetal weight discordance ≥ 25% were the principal predictors of C-SNM. A significant interaction was observed ( P = .003): the odds of C-SNM increased by approximately 80% per additional week among pregnancies with discordance < 25% and by approximately 30% among pregnancies with discordance ≥ 25%. Lower gestational age and greater discordance were also associated with worse CoMB and higher CMB, whereas dichorionicity was associated with lower morbidity burden. For DSM, discordance was most strongly associated with respiratory morbidity. Pregnancy-level composite assessment may refine risk stratification and strengthen prenatal counseling.