Obesity candidate genes, gestational weight gain, and body weight changes in pregnant women

To examine the associations of two obesity-associated genes, FTO (rs9939609) and GNB3 (rs5443) single nucleotide polymorphisms (SNPs), with early pregnancy body mass index, gestational weight gain, and postpartum weight retention.

Secondary data analysis of self-identified white (n = 580) and black (n = 194) women who participated in a randomized controlled trial (2009-2014) and provided a saliva sample of DNA. Bivariate relationships were assessed using analysis of variance. Multiple regression models assessed the relationship between outcomes and gene SNPs, controlling for income, parity, and smoking status.

FTO and GNB3 gene associations with pregnancy weight were different by racial group and early pregnancy body mass index. Obese black women homozygote for the FTO risk allele (AA) had a higher gestational weight gain compared with non-risk homozygotes (TT) (P = 0.006). GNB3 non-risk CC homozygotes tended to have a lower gestational weight gain compared with heterozygotes (P = 0.05). White GNB3 C carriers tended to be heavier in early pregnancy (P <0.1) and GNB3 homozygote (TT) overweight women tended to have lower postpartum weight retention than C carriers.

The FTO gene and possibly the GNB3 gene are associated with high gestational weight gain in obese black women. Obese carriers of the FTO risk allele gained 4.1 kg (AT) and 7.6 kg (TT) more than those without risk alleles. Overweight GNB3 heterozygotes (CT) gained 6.6 kg less than homozygotes (CC). Overweight or obese black women who have either risk variant are at risk for high gestational weight gain.