title: Vitamin D and assisted reproduction technologies: current concepts.
abstract: Accumulating evidence from animal and human studies suggests that vitamin D is involved in many functions of the human reproductive system in both genders, but no comprehensive analysis of the potential relationship between vitamin D status and Assisted Reproduction Technologies (ART) outcomes is currently available. On this basis, the purpose of this systematic review and meta-analysis was to perform an in-depth evaluation of clinical studies assessing whether vitamin D status of patients undergoing ART could be related to cycle outcome variables. This issue is of interest considering that vitamin D deficiency is easily amenable to correction and oral vitamin D supplementation is cheap and without significant side effects. Surprisingly, no studies are currently available assessing vitamin D status among male partners of couples undergoing ART, while seven studies on vitamin D status of women undergoing controlled ovarian hyperstimulation (COH) for ART were found and included in the review. Results show that vitamin D deficiency is highly prevalent among women undergoing COH, ranging from 21% to 31% across studies conducted in Western countries and reaching 75-99% in Iranian studies. Data on vitamin D deficiency (25-hydroxyvitamin D serum levels <20 ng/ml) in relation to ART outcomes could be extracted from three studies and included in the meta-analysis, yielding a common risk ratio (RR) of 0.89 (95% CI 0.53-1.49) and showing a lower but not statistically significant likelihood of clinical pregnancy for vitamin-D-deficient women compared with vitamin-D-sufficient patients. In conclusion, there is insufficient evidence to support the routine assessment of vitamin D status to predict the clinical pregnancy rate in couples undergoing ART. The partly conflicting results of the available studies, potentially explaining the lack of statistical significance for a negative influence of vitamin D deficiency on clinical pregnancy rate, are likely secondary to confounders and insufficient sample size, and further larger cohort and randomised controlled studies are required.
authors.forename: Valeria S
authors.initials: VS
authors.lastname: Vanni
authors.affiliation: Department Obstetrics and Gynecology, San Raffaele Scientific Institute, Via Olgettina 60, 20136 Milano, Italy. vigano.paola@hsr.it.
authors.forename: Paola
authors.initials: P
authors.lastname: Vigano'
authors.forename: Edgardo
authors.initials: E
authors.lastname: Somigliana
authors.forename: Enrico
authors.initials: E
authors.lastname: Papaleo
authors.forename: Alessio
authors.initials: A
authors.lastname: Paffoni
authors.forename: Luca
authors.initials: L
authors.lastname: Pagliardini
authors.forename: Massimo
authors.initials: M
authors.lastname: Candiani
mesh_terms: D000818:Animals; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D007247:Infertility, Female / Q000209:etiology* / Q000517:prevention & control / Q000628:therapy; D007248:Infertility, Male / Q000209:etiology* / Q000517:prevention & control; D008297:Male; D009752:Nutritional Status; D011247:Pregnancy; D011256:Pregnancy Outcome; D018873:Pregnancy Rate; D015995:Prevalence; D015203:Reproducibility of Results; D027724:Reproductive Techniques, Assisted; D055101:Semen Analysis; D014807:Vitamin D / Q000627:therapeutic use; D014808:Vitamin D Deficiency / Q000178:diet therapy / Q000453:epidemiology / Q000503:physiopathology*
chemical_list: D014807:Vitamin D