Are gestational diabetes mellitus and preconception diabetes mellitus less common in non-Hispanic black women than in non-Hispanic white women?

Based on their higher risk of type 2 diabetes, non-Hispanic blacks (NHBs) would be expected to have higher gestational diabetes mellitus (GDM) risk compared to non-Hispanic whites (NHWs). However, previous studies have reported lower GDM risk in NHBs versus NHWs. We examined whether GDM risk was lower in NHBs and NHWs, and whether this disparity differed by age group. The cohort consisted of 462,296 live singleton births linked by birth certificate and hospital discharge data from 2004 to 2007 in Florida. Using multivariable regression models, we examined GDM risk stratified by age and adjusted for body mass index (BMI) and other covariates. Overall, NHBs had a lower prevalence of GDM (2.5 vs. 3.1%, p < 0.01) and a higher proportion of preconception DM births (0.5 vs. 0.3%, p ≤ 0.01) than NHWs. Among women in their teens (risk ratio 0.56, p < 0.01) and 20-29 years of age (risk ratio 0.85, p < 0.01), GDM risk was lower in NHBs than NHWs. These patterns did not change with adjustment for BMI and other covariates. Among women 30-39 years (risk ratio 1.18, p < 0.01) and ≥40 years (risk ratio 1.22, p < 0.01), GDM risk was higher in NHBs than NHWs, but risk was higher in NHWs after adjustment for BMI. Associations between BMI and GDM risk did not vary by race/ethnicity or age group. NHBs have lower risk of GDM than NHWs at younger ages, regardless of BMI. NHBs had higher risk than NHWs at older ages, largely due to racial/ethnic disparities in overweight/obesity at older ages.