Newborn size among obese women with weight gain outside the 2009 Institute of Medicine recommendation.

OBJECTIVE: To estimate risk of delivering macrosomic, large-for-gestational-age and small-for-gestational-age neonates in obese women with gestational weight gain outside the 2009 Institute of Medicine recommendation (11-20 pounds).

METHODS: In a retrospective cohort study, we evaluated 2,080 obese women (body mass index 30 or higher) with singleton pregnancies that resulted in term live births within one health maintenance organization between 2000 and 2005; women with diabetes or hypertensive disorders were excluded. Gestational weight gain was categorized as less than 0, 0 to less than 11, 11-20 (referent), greater than 20-30, greater than 30-40, and greater than 40 pounds and as above, below, or within Institute of Medicine recommendations. We conducted multivariable logistic regression to estimate the odds of large for gestational age and small for gestational age (birth weights greater than the 90th percentile and less than the 10th percentile for gestational age, respectively) and macrosomia (greater than 4,500 g) adjusting for potential confounders.

RESULTS: Eighteen percent gained below, 25% within, and 57% above Institute of Medicine recommendations. Prevalence of macrosomia, large for gestational age, and small for gestational age were 4.3%, 19.8%, and 4.3%, respectively. Compared with weight gain of 11-20 pounds, weight gain above recommendations did not significantly decrease small-for-gestational-age risk but was associated with increased odds of macrosomia (adjusted odds ratio [OR] 3.36; 95% confidence interval [CI] 1.74-6.51; 6.0% compared with 2.1%) and large for gestational age (adjusted OR 1.80; 95% CI 1.36-2.38; 23.8% compared with 16.6%). Weight gain below recommendations was associated with increased odds of small for gestational age (adjusted OR 3.94; 95% CI 2.04-7.61; 8.8% compared with 2.7%) and decreased odds of large for gestational age (adjusted OR 0.56; 95% CI 0.37-0.84; 11.2% compared with 16.6%).

CONCLUSION: Regarding small for gestational age and large for gestational age, there is no benefit of weight gain above Institute of Medicine recommendations. Weight gain below recommendations decreases large for gestational age but increases small-for-gestational-age risk.

LEVEL OF EVIDENCE: II.