High pregnancy weight gain and risk of excessive fetal growth.

OBJECTIVE: The purpose of this study was too assess whether prepregnancy body mass index (BMI) modifies the relationship between pregnancy weight gain and large for gestational age (LGA; > 90% of birthweight for gestational age) or macrosomia (>or= 4500 g).

STUDY DESIGN: This was a population-based cohort study of 104,980 singleton, term births from 2000-2005.

RESULTS: Prepregnancy BMI modified the relationship between weight gain and LGA. Lean women had higher odds of LGA than overweight or obese women for weight gain >or= 36 lb. For macrosomia, prepregnancy BMI did not modify the association. Compared with women who gained 15-25 lb, the aOR for a gain of 26-35 lb was 1.5 (95% confidence interval [CI], 1.2-1.9), for a gain of 36-45 lb was 2.1 (95% CI, 1.7-2.7), and for a gain of >or= 46 lb was 3.9 (95% CI, 3.0-5.0).

CONCLUSION: Current pregnancy weight gain recommendations include weight gain ranges that are associated with increased risk of LGA and macrosomia.