Weight gain in twin gestations: are the Institute of Medicine guidelines optimal for neonatal outcomes?

OBJECTIVE: To assess neonatal outcomes according to gestational weight gain (GWG) in twins. STUDY DESIGN: This was a retrospective cohort study of twins delivered at >= 24 weeks. GWG was defined using the Institute of Medicine (IOM) guidelines as the referent. Birthweight and neonatal intensive-care unit (NICU) admissions were compared with chi(2)- and analysis of variance tests, stratified by body mass index (BMI). RESULT: In all three BMI groups, mean birth weight of the larger and smaller twin increased as GWG increased, P<0.01. For the underweight/normal-weight group, both twins <2500 g, <1500 g and small for gestational age decreased significantly as GWG increased. Birthweight <2500 g increased in all groups with GWG below the IOM guidelines, P<0.01. In the multivariate analysis, both twins <2500 g were significantly decreased with GWG above IOM guidelines. There was no difference in NICU admissions with GWG above the IOM guidelines. CONCLUSION: GWG above the IOM guidelines may improve twin birth weights, with the findings most significant in underweight/normal-weight women.