The impact of first-trimester vitamin D levels on gestational diabetes mellitus

INTRODUCTION: This study investigated the association between first-trimester 25-hydroxyvitamin D levels and the development of gestational diabetes mellitus (GDM) in a Turkish population.
METHODS: A retrospective cohort study was conducted with 458 pregnant women attending Ankara University Faculty of Medicine. First-trimester plasma vitamin D levels were recorded. GDM was diagnosed between 24-28 weeks using a two-step oral glucose tolerance test (OGTT) based on Carpenter-Coustan criteria. Binary logistic regression was used to identify independent risk factors.
RESULTS: The prevalence of GDM was 9.8%, while 86% of the population had vitamin D deficiency (<20 ng/mL). There was no statistically significant difference in vitamin D levels between women with and without GDM (p>0.05). Multivariate analysis confirmed that advanced maternal age and higher body mass index (BMI) were independent risk factors, whereas first-trimester vitamin D levels showed no significant association with GDM.
DISCUSSION AND CONCLUSION: In this cohort characterized by widespread vitamin D deficiency and routine supplementation, first-trimester vitamin D levels did not serve as an independent predictor for GDM development. While age and BMI remain significant predictors, early vitamin D screening may have limited predictive value for GDM in this specific population.

Keywords: Gestational diabetes mellitus, Vitamin D deficiency, Pregnancy, Insulin resistance, Risk factors