Association Between Vitamin D Level and Clinical Outcomes of Assisted Reproductive Treatment: A Systematic Review and Dose-Response Meta-Analysis

Systematic review and dose-response meta-analysis of women undergoing assisted reproductive treatment, including IVF and ICSI, with vitamin D measured in serum or follicular fluid. Included studies covered diverse populations and settings, with subgroup analyses by Asian and non-Asian groups and both autologous and donor-oocyte contexts.

Vitamin D exposure was evaluated as serum or follicular fluid vitamin D status in women undergoing assisted reproductive treatment, categorized across included studies as deficient, insufficient, and sufficient. This review did not test a supplementation regimen; it compared reproductive outcomes across vitamin D status groups and examined a dose-response relationship.

Overall, higher vitamin D status was associated with better assisted reproductive outcomes, especially clinical pregnancy and live birth. Deficient vitamin D versus non-deficient status was associated with lower clinical pregnancy rate (OR 0.81, 95% CI 0.70–0.95, P = 0.01) and live birth rate (OR 0.69, 95% CI 0.54–0.89, P = 0.003). Deficient plus insufficient vitamin D versus sufficient vitamin D was also associated with lower clinical pregnancy rate (OR 0.71, 95% CI 0.55–0.91, P = 0.007) and live birth rate (OR 0.69, 95% CI 0.54–0.89, P = 0.003). Biochemical pregnancy, ongoing pregnancy, miscarriage, and implantation rates were not consistently associated with vitamin D status. The dose-response analysis suggested a nonlinear relationship, with little effect below about 24 ng/L and stronger favorable associations above that threshold.

The evidence is based on observational studies rather than randomized trials, so confounding and reverse causation remain possible. Exposure definitions varied across studies, heterogeneity was present, and subgroup findings may not generalize across populations or ART settings. The proposed 24 ng/L threshold is hypothesis-generating and requires confirmation in larger prospective studies and randomized trials.