The Association between Maternal B Vitamins in Early Pregnancy and Gestational Diabetes Mellitus: A Prospective Cohort Study

Background: This study evaluated the association between maternal B vitamins in early pregnancy and gestational diabetes mellitus (GDM) risk. Methods: A cohort of 1265 pregnant women was recruited at 8–15 weeks of gestation in 2021–2022 (Shanghai, China). Pregnancies with both serum B vitamin measurements at recruitment and glucose measurements at 24–28 weeks of gestation were included in the final analysis. Results: Of the 1065 pregnancies, in the final analysis, GDM occurred in 121 women (11.36%). In multivariate logistic models, an increased risk trend across serum vitamin B(1) quartiles with GDM was observed (p-Trend = 0.001). Compared with women in the lowest quartile of serum vitamin B(6), those in the upper two quartiles had approximately twofold higher odds of GDM. Moreover, compared with women with vitamin B(12) levels < 150 pmol/L, those with vitamin B(12) levels > 150 pmol/L had lower odds of GDM (p = 0.005). The restricted cubic spline regression models also revealed that serum vitamin B(6) and vitamin B(12) were associated with an increased risk of GDM in a nonlinear fashion. Conclusions: Our study shows that higher maternal serum vitamin B(1) and B(6) levels in early pregnancy are associated with increased GDM risk, while sufficient vitamin B(12) status is associated with lower GDM risk.