Pre-pregnancy weight and excess weight gain are risk factors for macrosomia in women with gestational diabetes

Objective: To determine whether women with gestational diabetes mellitus (GDM) whose weight gain exceeded the 2009 Institute of Medicine (IOM) recommendations were more likely to have macrosomia. Study Design: Retrospective cohort study of the association of weight gain in women with Class A1 GDM, with term (<= 37 weeks) singleton liveborns and macrosomia (birthweight <= 4000 g). Multivariate logistic regression models were used to adjust for covariates and test for interactions. Result: Of 1502 women studied, pre-pregnancy body mass index (BMI) categories were: normal (39.6%), overweight (28.5%) and obese (31.9%). The mean (+/- standard deviation) weight gain (lbs) for these groups was: 27.6 +/- 10.9, 24.2 +/- 13.0 and 18.8 +/- 16.3 (P<0.0001), whereas the occurrence of macrosomia was 7.4, 11.4 and 19.0%, respectively. Women with an obese BMI were twice as likely to have a macrosomic infant compared with women in the normal BMI group (odds ratio, OR 2.0; 95% CI 1.4-3.0; P=0.0005). Independently, women who exceeded the IOM guidelines were three times more likely to have a macrosomic infant (OR 3.0, 95% CI 2.2-4.2, P<0.0001). Conclusion: Maternal pre-pregnancy weight and weight gain during pregnancy appear to be significant and independent risk factors for macrosomia in women with GDM. Journal of Perinatology (2011) 31, 717-721; doi:10.1038/jp.2011.15; published online 3 March 2011