Association of trimester-specific gestational weight gain with child BMI by maternal BMI categories

Background/Objectives: Information is lacking about how trimester-specific gestational weight gain (GWG) is associated with childhood body mass index (BMI) across maternal BMI categories. Subjects/Methods: We examined the association between GWG and child BMI in patients served by a national network of community health care organizations. We stratified by pre-pregnancy BMI (n=5721 normal weight; 5667 overweight; 3213 obesity class I; 1344 class II; 692 class III). Child BMI z-score and overweight and obesity status at age 5 were modeled as a function of total GWG and GWG rate in each trimester, controlling for GWG rate in previous trimester(s) and maternal characteristics, using modified Poisson regression. Results: Higher total GWG during pregnancy was positively associated with child BMI at 5 years of age in a linear, dose-dependent manner. When examined by trimester of pregnancy, a 1 kg/week in the first trimester was associated with a 0.24 to 0.42 increase in child BMI z-score. The same increase in the second trimester was associated with a 0.30 to 0.53 increase in child BMI z-score, although the associations were not significant in class II and III obesity classes. Associations between GWG in the third trimester and child BMI z-score were weak (0.12 to 0.21 increase in BMI z-score per kg/week increase in maternal weight) and not significant. Conclusion: Among a diverse and underserved pregnant population, GWG in the 1 ^st and 2 ^nd trimesters are most strongly associated with child BMI at age 5. Early pregnancy and mid-pregnancy may be key times to intervene to prevent overweight and obesity in offspring.