Objective: To assess the clinical significance of twin intrapair birth weight differences.
Methods: This was a retrospective study of twin pregnancy outcomes. Intrapair birth weight differences were stratified into the following six groups: 14% or less, 15-20%, 21-25%, 26-30%, 31-40%, and 41% or more using the larger infant as the growth standard. Statistical analysis was done using the Mantel-Haenzel chi2 test.
Results: We studied 1370 consecutive women who delivered at Parkland Hospital, Dallas, Texas, between January 1, 1988, and December 31, 1996, and had twin gestations and live births or fetal deaths within 7 days of delivery. Greater birth weight discordance was significantly associated with preterm delivery due to intervention (P<.001). Noncephalic-cephalic presentations and cesarean delivery were also associated with greater discordance (P = .001 and .02, respectively). Neonatal morbidities, including low birth weight, intensive care admission, and respiratory distress, were all associated with higher birth weight discordance. Fetal abnormalities were more common with increased discordance (P<.001). Greater birth weight discordance was also associated with intrauterine fetal death. There were no differences in outcome for the smaller compared with the larger twin of the twin pair.
Conclusion: Twin birth weight discordance is problematic because severe divergent fetal growth increases the risk of fetal death and leads to obstetric intervention and consequent neonatal morbidity due to prematurity.