The present study sought to examine the association between dietary Ca intake and risk of gestational diabetes mellitus (GDM).

We assessed periconceptional (i.e. before conception and early pregnancy) Ca intake and consumption of foods rich in Ca using an FFQ among 3414 participants in a prospective cohort study. Diagnoses of GDM were abstracted from medical records. We used multivariable generalized linear regression models to derive estimates of relative risk (RR) for GDM and 95 % confidence intervals.

A prospective cohort of women in Seattle and Tacoma, WA, USA.

Women (n 3414).

A total of 169 GDM incident cases were identified in the cohort (4·96 %). Higher dietary Ca intake was inversely, although not statistically significantly, associated with GDM risk. After adjusting for confounders, the RR (95 % CI) for GDM according to successive increasing quartile of Ca intake was 1·00, 0·63 (0·41, 0·98), 0·66 (0·39, 1·11) and 0·57 (0·27, 1·21), respectively, with the lowest quartile as the reference (Ptrend=0·131). Compared with women in the first quartile for Ca intake, women in the higher three quartiles (≥795 v. <795 mg/d) had a 42 % (RR=0·58; 95 % CI 0·38, 0·90; P=0·015) lower GDM risk. GDM risk was inversely associated with low-fat dairy (Ptrend=0·032) and whole grains (Ptrend=0·019) consumption.

These findings suggest that higher levels of periconceptional Ca intake, particularly intake of Ca-rich low-fat dairy products and whole grains, are associated with lower GDM risk.