Serum 25-hydroxyvitamin D concentrations and treatment outcomes of women undergoing assisted reproduction

Vitamin D deficiency impairs fertility in animal models, but the role of vitamin D in human fertility or treatment of infertility is less clear. We examined the association between circulating 25-hydroxyvitamin D [25(OH)D] concentrations and the outcome in women undergoing assisted reproduction technologies (ARTs). We randomly selected 100 women undergoing infertility treatment with ART enrolled in an ongoing prospective cohort study who underwent 168 treatment cycles. Serum 25(OH)D concentrations were measured in samples collected from women between days 3 and 9 of gonadotropin treatment. Generalized linear mixed models were used to evaluate the association of 25(OH)D concentrations with ART outcomes while adjusting for potential confounders and accounting for repeated treatment cycles per woman. Median (range) serum 25(OH)D concentrations were 86.5 (33.5-155.5) nmol/L. Ninety-one percent of participants consumed multivitamins. Serum 25(OH)D concentrations were positively related to fertilization rate. The adjusted fertilization rate for women in increasing quartiles of serum 25(OH)D were 0.62 (95% CI: 0.51, 0.72), 0.53 (95% CI: 0.43, 0.63), 0.67 (95% CI: 0.56, 0.76), and 0.73 (95% CI: 0.63, 0.80), respectively (P-trend = 0.03). This association persisted when analyses were restricted to women with serum 25(OH)D between 50 and 125 nmol/L when models were further adjusted for season of blood draw and when analyses were restricted to the first treatment cycle. However, 25(OH)D concentrations were unrelated to probability of pregnancy (P-trend = 0.83) or live birth after ART (P-trend = 0.47). Vitamin D may be associated with higher fertilization rates, but this apparent benefit does not translate into higher probability of pregnancy or live birth. This trial was registered at www.clinicaltrials.gov as NCT00011713.