Association Between the Concentration of Serum Vitamin D and Ovarian Reserve Among Women Undergoing Assisted Reproductive Technology.

Background: Multiple in vivo and in vitro studies have demonstrated that 25-OH vitamin D has a significant positive effect on ovarian reserve in women; however, findings from population-based studies have been inconsistent.

Objectives: This study aimed to evaluate whether there is an association between serum 25-OH vitamin D concentrations and ovarian reserve.

Methods: A cross-sectional study was conducted with 1488 women aged 20-50 y undergoing assisted reproductive treatment. Antimüllerian hormone, antral follicle count (AFC), and follicle-stimulating hormone (FSH) are used as markers of ovarian reserve. Diminished ovarian reserve is defined by low concentrations of antimüllerian hormone (≤1.1 ng/mL), high concentrations of FSH (≥10 IU/L), or low concentrations of AFC (≤7). Poisson regression, multiple linear regression, logistic regression, and restricted cubic spline (RCS) models were used to assess the association between 25-OH vitamin D and ovarian reserve biomarkers, as well as risk of diminished ovarian reserve.

Results: In the Poisson regression model, we found a significant positive correlation between vitamin D and AFC (β: 0.003; 95% CI: 0.001, 0.005). Moreover, BMI demonstrated a significant interaction effect in the association between 25-hydroxyvitamin D and AFC concentrations (P-interaction = 0.03). Stratified analyses further revealed that the positive association between vitamin D and AFC was only observed among individuals with lower BMI (<24 kg/m²), whereas no significant association was found in the higher BMI group. Additionally, we also identified a significant nonlinear relationship between 25-OH vitamin D and FSH (P-nonlinear < 0.05).

Conclusions: 25-Hydroxyvitamin D is associated with higher AFC concentrations, and FSH exhibits an inverted U-shaped trend as vitamin D concentration increase. These findings suggest that 25-OH vitamin D may have a potential positive role in maintaining female ovarian health.