Is discordant growth in twins an independent risk factor for adverse neonatal outcome?

To estimate whether discordant growth is associated with adverse perinatal outcomes in twins after adjusting for growth restriction.

This was a retrospective, hospital-based cohort study of twin gestations with 2 live births delivered at 24 weeks or later from 1992 to 2001. Twin gestations were classified as small for gestational age (SGA) if one or both infants was less than the 10th percentile at birth by singleton Brenner norms and discordant if there was a 20% or more weight discordance.

Of 1318 twin pairs, 856 were appropriate for gestational age (AGA) and concordant, 70 pairs were AGA and discordant, 254 pairs were SGA and concordant, and 138 pairs were SGA and discordant. The 4 groups had similar maternal demographics and medical comorbidity. When adjusting for chorionicity, antenatal steroid use, oligohydramnios, preeclampsia, and gestational age at delivery, discordant twins were more likely to have a cesarean delivery (odds ratio 1.87; 95% confidence interval 1.22, 2.87) and to be associated with some adverse neonatal outcomes (low and very low birthweight, neonatal intensive care unit admission, neonatal oxygen requirement and hyperbilirubinemia) independent of SGA status. A statistically nonsignificant trend (odds ratio 2.4; 95% confidence interval 0.99, 6.01) toward higher rates of intraventricular hemorrhage was noted in discordant twins, and no difference was seen for ventilator requirement, respiratory distress syndrome, or necrotizing enterocolitis.

Discordance places twins at increased risk for some adverse perinatal outcomes, whether they are AGA or SGA. Discordance was not an independent risk factor for serious neonatal morbidity or mortality; however, this study was underpowered to detect those differences.