AbstractBackgroundThe ABO blood types are associated with cancers, cardiovascular diseases and type 2 diabetes mellitus but whether they are also associated with gestational diabetes mellitus (GDM) is unknown. We examined the relationship between the ABO blood types and the risk of GDM in a prospective population‐based Chinese cohort.MethodsFrom 2010 to 2012, we recruited 14 198 pregnant women within the first 12 weeks of gestation in Tianjin, China. All women had a glucose challenge test (GCT) at 24–28 gestational weeks, followed by a 75‐g 2‐h oral glucose tolerance test if the results from GCT were ≥7.8 mmol/L. GDM was diagnosed based on the glucose cut‐points of the International Association of Diabetes and Pregnancy Study Group criteria. Logistic regression was used to obtain odds ratios (ORs) and 95% confidence intervals (CIs) adjusted for traditional risk factors. Stratified analysis was performed by family history of diabetes (yes versus no). Sensitivity analyses were also performed by using the World Health Organization (WHO) criteria for GDM.ResultsWomen with blood groups A, B or O (i.e. non‐AB) were associated with increased risk of GDM as compared with those with blood group AB (adjusted OR: 1.44, 95% CI: 1.13–1.83). Sensitivity analyses showed that the result was consistent using WHO criteria. The adjusted OR of blood group non‐AB versus AB for GDM was enhanced among women with a family history of diabetes (2.69, 1.21–5.96) and attenuated among those without (1.33, 1.03–1.71).ConclusionsBlood group AB was a protective factor against GDM in pregnant Chinese women. Copyright © 2015 John Wiley & Sons, Ltd.