Early Pregnancy Weight Gain Exerts the Strongest Effect on Birth Weight, Posing a Critical Time to Prevent Childhood Obesity

Objective: Gestational weight gain (GWG) is associated with infant birth weight and childhood obesity; however, the patterns of GWG on infant birth weight are poorly understood. Methods: This analysis in 16,218 mother-child dyads from Tianjin, China, determined the risk of infant size at birth according to GWG occurring throughout the first and second trimester (early GWG) or during the third trimester (late GWG), according to maternal prepregnancy BMI and the 2009 Institute of Medicine recommendations. Results: Excessive GWG in early and late pregnancy had an increased risk for large-for-gestational-age (LGA) infants (odds ratio [OR]: 2.4; 95% confidence interval [CI]: 1.5-4.0, P < 0.001). Regardless of prepregnancy BMI, excessive GWG early in pregnancy (< 24 weeks) was associated with an increased risk of LGA infants (OR: 2.5; 95% CI: 2.1-3.1, P < 0.001), and inadequate early GWG was associated with a higher risk of small-for-gestational-age (SGA) infants (OR: 1.4; 95% CI: 1.2-1.7, P < 0.001). Conclusions: The pattern of GWG early in pregnancy, regardless of GWG later in pregnancy, had the greatest impact on infant size at birth. Interventions initiated early in pregnancy may facilitate better adherence to the GWG guidelines and minimize the risk of LGA and SGA infants, a potential precursor for childhood obesity.