Background: Vitamin D, calcium, and magnesium play complementary roles in female reproductive physiology, yet evidence regarding their combined association with infertility remains limited in sub-Saharan Africa. This study compared serum concentrations of these micronutrients between fertile and infertile women attending a tertiary hospital in northwestern Nigeria and evaluated factors associated with their levels.

Methods: A hospital-based comparative cross-sectional study was conducted among 200 women (100 infertile and 100 fertile) attending Usmanu Danfodiyo University Teaching Hospital, Sokoto. Sociodemographic and clinical data were collected using structured questionnaires. Serum 25-hydroxyvitamin D, calcium, and magnesium concentrations were measured using standardized laboratory methods. Comparisons between groups were performed using the Mann–Whitney U test, while multivariable logistic regression identified independent determinants of micronutrient levels.

Results: Infertile women had significantly lower mean serum vitamin D (27.80 ± 2.30 vs. 29.68 ± 1.48 ng/mL), calcium (1.93 ± 0.25 vs. 2.12 ± 0.25 mmol/L), and magnesium (0.55 ± 0.08 vs. 0.68 ± 0.11 mmol/L) than fertile women (all p < .001). After adjustment for potential confounders, fertility status remained an independent predictor of serum vitamin D, calcium, and magnesium concentrations. Significant associations were also observed among vitamin D, calcium, and magnesium, demonstrating their physiological interdependence.

Conclusions: Infertile women exhibited significantly lower serum vitamin D, calcium, and magnesium concentrations than fertile women. The observed interrelationships among these micronutrients support their integrated role in female reproductive function. Routine nutritional assessment may represent a useful adjunct to infertility evaluation, while prospective and interventional studies are required to determine whether correction of micronutrient deficiencies improves fertility outcomes.

Keywords: infertility; vitamin D; calcium; magnesium; female fertility; micronutrients; Nigeria.