Interaction between maternal prepregnancy body mass index and gestational weight gain shapes infant growth

To quantify the combined effect of maternal prepregnancy obesity and maternal gestational weight gain (GWG) on the shape of infant growth throughout the first year of life.

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.

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 BMI (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 kg/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).

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.