Association of trimester-specific gestational weight gain with child BMI by maternal BMI categories in community-based healthcare organizations.

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 receiving care from 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 linear or 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 stratified by BMI, each 1 kg/week greater weight gain in the first trimester was associated with a 0.25-0.45 increase in child BMI z-score, depending on BMI class. Each 1 kg/week weight gain in the 2nd trimester was associated with a 0.28 to 0.52 increase in child BMI z-score, although the associations were not significant in class III obesity. Associations between GWG in the third trimester and child BMI z-score were weak (-0.07 to 0.21 increase in BMI z-score per kg/week increase in maternal weight) and generally not significant. CONCLUSION: Among a diverse and systemically underserved pregnant population, GWG in the 1st and 2nd 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.