Higher Pre-pregnancy BMI and Excessive Gestational Weight Gain are Risk Factors for Rapid Weight Gain in Infants

Abstract

Objective To describe the effects of maternal pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) on infant anthropometrics at birth and 3 months and infant growth rates between birth and 3 months. Methods Body weight prior to and during pregnancy and infant weight and length at birth and 3 months were collected from 600 mother-infant pairs. Adherence to GWG was based on IOM recommendations. Age and sex specific z-scores were calculated for infant weight and length at birth and 3 months. Rapid postnatal growth was defined as a difference of >0.67 in weight-for-age z-score between birth and 3 months. Relationships between maternal and infant characteristics were analysed using multilinear regression. Results Most women (65%) had a normal pre-pregnancy BMI and 57% gained above GWG recommendations. Infants were 39.3 ± 1.2 weeks and 3431 ± 447.9 g at birth. At 3 months postpartum 60% were exclusively breast fed while 38% received breast milk and formula. Having a pre-pregnancy BMI >25 kg/m² was associated with higher z-scores for birth weight and weight-for-age at 3 months. Gaining above recommendations was associated with higher z-scores for birth weight, weight-for-age and BMI. Infants who experienced rapid postnatal growth had higher odds of being born to women who gained above recommendations. Conclusion for Practice Excessive GWG is associated with higher birth weight and rapid weight gain in infants. Interventions that optimize GWG should explore effects on total and rates of early infant growth.

Keywords: Birth weight z-score; Gestational weight gain; Pre-pregnancy BMI; Weight-for-age z-score.