BMI and season are associated with vitamin D deficiency in women with impaired fertility: a two-centre analysis.

PURPOSE: Animal and human studies suggest that vitamin D regulates functions of the reproductive system. Vitamin D deficiency is prevalent in women of reproductive age. Vitamin D status has been associated with in vitro fertilisation outcome, features of polycystic ovarian syndrome (PCOS) and endometriosis. The aims of our study were to investigate the prevalence of vitamin D deficiency of infertile women living in central Germany, to identify risk factors for vitamin D deficiency and to specify seasonal variations of vitamin D status.

METHODS: This was a retrospective cohort study at an academic tertiary care centre (N = 113) and an Outpatient Centre for Reproductive Medicine (N = 193) of women presenting for infertility treatment. The statistical evaluation was descriptive and explorative. Possible risk factors associated with an increased risk for vitamin D deficiency were assessed using multiple logistic regression models. Variables with p value less than 0.05 were further assessed in a multivariable logistic regression model.

RESULTS: Overall, 98.2 % of patients at centre 1 and 81.3 % of women with impaired fertility at centre 2 had deficient or insufficient vitamin D levels. Overweight BMI and limited exposure to sun (winter, spring and autumn trimester) were associated with an increased risk of vitamin D deficiency. Vitamin D levels did not vary according to age or infertility associated disorders (e.g. endometriosis, PCOS).

CONCLUSION: The rate of vitamin D deficiency among women with impaired fertility is alarming. Prospective studies are pressingly needed to confirm a causal relationship and to investigate the potential therapeutic benefits of vitamin D supplementation in this population.