Prepregnancy weight, gestational weight gain, and risk of growth affected neonates

In 2009, the Institute of Medicine published revised gestational weight gain (GWG) guidelines with changes notable for altered body mass index (BMI) categorization as per World Health Organization criteria and a stated range of recommended gain (11-20 pounds) for obese women. The goal of this study was to evaluate associations between maternal BMI-specific GWG adherence in the context of these new guidelines and risk of small for gestational age (SGA) and large for gestational age (LGA) neonates.

Subjects were a retrospective cohort of 11,203 live birth singletons delivered at 22-44 weeks at a Massachusetts tertiary care center between April 2006 and March 2010. Primary exposure was GWG adherence (inadequate, appropriate, or excessive) based on BMI-specific recommendations. SGA and LGA were defined as <10th and ≥90th percentiles of U.S. population growth curves, respectively. The association between GWG adherence and SGA and LGA was examined in polytomous logistic regression models that estimated adjusted odds ratios (AOR) stratified by prepregnancy weight status, controlling for potential confounders.

Before pregnancy, 3.8% of women were underweight, 50.9% were normal weight, 24.6% were overweight, and 20.6% were obese. Seventeen percent had inadequate GWG, and 57.2% had excessive GWG. Neonates were 9.6% SGA and 8.7% LGA. Inadequate GWG was associated with increased odds of SGA (AOR 2.51, 95% confidence interval [CI] 1.31-4.78 for underweight and AOR 1.78, 95% CI 1.42-2.24 for normal weight women) and decreased odds of LGA (AOR 0.5, 95% CI 0.47-0.73 for normal weight and AOR 0.56, 95% CI 0.34-0.90 for obese women). Excessive GWG was associated with decreased odds of SGA (AOR 0.59, 95% CI 0.47-0.73 for normal weight and AOR 0.64, 95% CI 0.47-0.89 for overweight women) and increased odds of LGA (AOR 1.76, 95% CI 1.38-2.24 for normal weight, AOR 2.99, 95% CI 1.92-4.65 for overweight, and AOR 1.55, 95% CI 1.10-2.19 for obese women).

Efforts to optimize GWG are essential to reducing the proportion of SGA and LGA neonates, regardless of prepregnancy BMI.