Gestational Weight Gain and Maternal and Neonatal Outcomes in Underweight Pregnant Women: A Population-Based Historical Cohort Study.

Objective Limited data are available that estimate the effect of gestational weight gain on maternal and neonatal outcomes in underweight women according to revised 2009 Institute of Medicine (IOM) guidelines. Methods A population-based historical cohort study of 21,674 underweight women in Missouri delivering liveborn, singleton, term infants in 2002-2008 was conducted. Adjusted odds ratios were calculated for gestational weight gain categories with multiple logistic regression, using the 2009 IOM recommended 28-40 pounds as the reference group. Results Women gaining >40 pounds compared to women gaining 28-40 pounds had significantly higher odds for preeclampsia (aOR 1.94, 95% CI 1.56-2.42, p < 0.001), cesarean delivery (aOR 1.40, 95% CI 1.28-1.53, p < 0.001), large-for-gestational-age (LGA) infant (aOR 2.32, 95% CI 2.00-2.70, p < 0.001), and 1 min APGAR score <4 (aOR 1.36, 95% CI 1.01-1.83, p < 0.05) and significantly lower odds for small-for-gestational-age (SGA) infant (aOR 0.53, 95% CI 0.48-0.59, p < 0.001). Women gaining <28 pounds compared to women gaining 28-40 pounds had significantly higher odds for SGA infant (aOR 1.85, 95% CI 1.69-2.03, p < 0.001) and significantly lower odds for preeclampsia (aOR 0.72, 95% CI 0.53-0.96, p < 0.05) and LGA infant (aOR 0.50, 95% CI 0.39-0.63, p < 0.001). Conclusion Women gaining more than the IOM recommendation were at higher risk for many adverse outcomes, but at lower risk for SGA infants. Women gaining less than the IOM recommendation were at higher risk for SGA infants but were protective for preeclampsia and LGA infants. Prospective studies of other short- and long-term maternal/infant outcomes are needed to evaluate the efficacy of the IOM guideline.