The Role of Vitamins in Preconception Care and Infertility Treatment: A Narrative Review

BackgroundMicronutrient supplementation is widely used in infertility care and preconception management, yet clinical evidence supporting its effectiveness differs among vitamins.MethodsThis narrative review summarizes current evidence on water- and fat-soluble vitamins in women undergoing infertility treatment, with an emphasis on assisted reproductive technology (ART) outcomes, biological mechanisms, and clinical relevance from a preconception care perspective.Main findingsAmong water-soluble vitamins, folate and vitamin B12 show the most consistent associations with ART outcomes, reflecting their central roles in one-carbon metabolism, DNA synthesis, and methylation. Genetic variation in folate metabolism, including methylenetetrahydrofolate reductase polymorphisms, may further modify reproductive outcomes and influence folate formulation choice. In contrast, clinical evidence for vitamins B6 and C remains limited despite biological plausibility. Vitamin D deficiency is highly prevalent among infertile women and has been associated with less favorable reproductive outcomes, although supplementation trials suggest modest and context-dependent benefits. Evidence supporting vitamin E or vitamin A use is largely confined to surrogate markers or specific phenotypes.ConclusionDespite biological plausibility and widespread use, current evidence does not support routine vitamin supplementation in infertility care. A targeted approach based on documented deficiencies and clinical phenotype is more appropriate.