Maternal BMI-Increasing Genetic Risk Score and Fetal Weights among Diverse US Ethnic Groups

Objective Associations between maternal genetic risk for obesity and fetal weight were examined at the end of the first (13 weeks 6 days), second (27 weeks 6 days), and third (40 weeks 0 days) trimesters of pregnancy among four race/ethnic groups in the US. Methods For 603 white, 591 black, 535 Hispanic, and 216 Asian women, maternal genetic risk score (GRS) was calculated as the sum of 189 BMI-increasing alleles and was categorized into high or low GRS. Associations between GRS (continuous and categorical) and estimated fetal weight were tested overall and stratified by prepregnancy BMI, gestational weight gain (GWG), and fetal sex. Results High GRS compared with low GRS was associated with increased fetal weight at the end of the second (beta: 22.7 g; 95% CI: 2.4-43.1; P = 0.03) and third trimesters (beta: 88.3 g; 95% CI: 9.0-167.6; P = 0.03) among Hispanic women. The effect of GRS was stronger among Hispanic women with normal prepregnancy weight, adequate first trimester GWG, or inadequate second trimester GWG (P < 0.05). Among Asian women, high GRS was associated with increased weight among male fetuses but decreased weight among female fetuses (P < 0.05). Conclusions Maternal obesity genetic risk was associated with fetal weight with potential effect modifications by maternal prepregnancy BMI, GWG, and fetal sex.