A population-based cohort study of the relation between maternal birthweight and risk of gestational diabetes mellitus in four racial/ethnic groups

Intrauterine growth retardation and low birthweight have been associated wi th an increased risk of insulin resistance and type II diabetes later in li fe. We hypothesised that maternal low birthweight is associated with an inc reased risk of gestational diabetes mellitus (GDM). Study subjects comprise d women giving birth in Washington State between 1987 and 1995. Information for 21528 births to non-Hispanic white women, 6359 to African-American wom en, 7456 to Native American women and 6496 to Hispanic women was available for analysis. All information was derived from statewide computerised vital records and hospital discharge summaries of obstetric and neonatal admissi ons with linkage to birth certificates of mothers. Maternal birthweight was collected from subjects' birth certificates. Information from both the bir th certificates and the obstetric and neonatal admissions database was used to determine whether subjects developed GDM. Poisson regression models wer e estimated to calculate unadjusted and adjusted risk ratios (RRs) and 95% confidence intervals (CIs) for GDM by categories of maternal birthweight. T he cumulative incidence of GDM among non-Hispanic white, African-American, Native American and Hispanic women was 2.8, 2.6, 2.7 and 3.0% respectively. After adjusting for maternal age, parity, cigarette smoking, history of ch ronic hypertension and participation in the Medicaid programme, non-Hispani c white women with a birthweight < 2000 g were 1.7 times more likely to hav e had their pregnancy complicated by GDM (RR = 1.7; 95% CI 0.8, 3.3) than t hose with a birthweight 3000-3999 g. The corresponding adjusted RRs for Afr ican-American, Native American, and Hispanic women were 2.8 [95% CI 1.2, 6. 1], 3.1 [95% CI 1.2, 8.2] and 2.4 [95% CI 0.9, 6.0] respectively. Among Afr ican-American women, those with a birthweight greater than or equal to 4000 g also experienced a twofold increased risk of GDM (RR = 2.1; 95% CI 1.0, 4.1). This association of high birthweight and increased GDM risk was not f ound among women in the other three racial/ethnic groups. These findings su ggest that individuals with low birthweight constitute a group at increased risk for GDM.