Interaction between Maternal Prepregnancy Body Mass Index and Gestational Weight Gain Shapes Infant Growth

OBJECTIVE: To quantify the combined effect of maternal pre-pregnancy obesity and maternal gestational weight gain (GWG) on the shape of infant growth throughout the first year of life. METHODS: A retrospective cohort of mother-child dyads with children born between January 2007 and May 2012 was identified in a linked electronic medical record. Data were abstracted to define the primary exposures of maternal prepregnancy body mass index (BMI) and GWG, and the primary outcome of infant growth trajectory. RESULTS: We included 499 mother-child dyads. The average maternal age was 28.2 years; 55% of mothers were overweight or obese before pregnancy, and 42% of mothers had excess GWG, as defined by the Institute of Medicine. Maternal prepregnancy BM1 (P < .001) and the interaction between prepregnancy BMI and maternal GWG (P = .02) showed significant association with infant growth trajectory through the first year of life after controlling for breast-feeding and other covariates, while GWG alone did not reach statistical significance (P = .38). Among infants of mothers with excess GWG, a prepregnancy BMI of 40 k g/m(2) versus 25 kg/m(2) resulted in a 13.6% (95% confidence interval 5.8, 21.5; P < .001) increase in 3-month infant weight/length percentile that persisted at 12 months (8.4%, 95% confidence interval 0.2, 16.5; P = .04). CONCLUSIONS: The combined effect of excess maternal GWG and prepregnancy obesity resulted in higher infant birth weight, rapid weight gain in the first 3 months of life, with a sustained weight elevation throughout the first year of life. These findings highlight the importance of the preconception and prenatal periods for pediatric obesity prevention.