Association Between Maternal Serum 25-Hydroxyvitamin D Concentrations and Gestational Diabetes Mellitus in Women Undergoing Diagnostic 100-g Oral Glucose Tolerance Testing.

Background

Gestational diabetes mellitus (GDM) is a common metabolic complication of pregnancy. Vitamin D has been implicated in glucose metabolism; however, its association with GDM remains controversial.

Objective

The objective was to evaluate the association between maternal serum 25-hydroxyvitamin D [25(OH)D] concentrations and GDM in pregnant women referred for diagnostic 100 g oral glucose tolerance testing following a positive 50 g glucose challenge test.

Methods

This retrospective study included 92 pregnant women (44 with GDM and 48 without GDM) who underwent diagnostic 100 g oral glucose tolerance testing between January 2016 and June 2025 at a tertiary-care hospital. Demographic characteristics and biochemical parameters, including serum 25(OH)D concentrations, were obtained from medical records. Logistic regression analysis was performed to identify factors independently associated with GDM.

Results

Women with GDM were significantly older than those without GDM (37.55 ± 6.06 vs. 29.21 ± 4.29 years, p < 0.001) and had lower serum vitamin D concentrations (14.08 ± 9.88 vs. 19.06 ± 10.30 ng/mL, p = 0.003). In multivariable logistic regression analysis, advanced maternal age (OR 1.404, 95% CI 1.217-1.620; p < 0.001) and lower serum vitamin D concentrations (OR 0.933, 95% CI 0.880-0.989; p = 0.020) were independently associated with GDM.

Conclusion

Lower maternal serum 25(OH)D concentrations were independently associated with GDM in women referred for diagnostic 100 g oral glucose tolerance testing. These findings should be interpreted as observational and hypothesis-generating. Larger prospective studies are needed to confirm these results.