Vitamin D and assisted reproductive treatment outcome: A systematic review and meta-analysis

STUDY QUESTION: Is serum vitamin D associated with live birth rates in women undergoing ART? SUMMARY ANSWER: Women undergoing ART who are replete in vitamin D have a higher live birth rate than women who are vitamin D deficient or insufficient. WHAT IS KNOWN ALREADY: Vitamin D deficiency has been associated with an increased risk of abnormal pregnancy implantation as well as obstetric complications such as pre-eclampsia and fetal growth restriction. However, the effect of vitamin D on conception and early pregnancy outcomes in couples undergoing ART is poorly understood. STUDY DESIGN, SIZE, DURATION: A systematic review and meta-analysis of 11 published cohort studies (including 2700 women) investigating the association between vitamin D and ART outcomes. PARTICIPANTS/MATERIALS, SETTINGS, METHODS: Literature searches were conducted to retrieve studies which reported on the association between vitamin D and ART outcomes. Databases searched included MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials and CINAHL. Eleven studies matched the inclusion criteria. MAIN RESULTS AND THE ROLE OF CHANCE: Live birth was reported in seven of the included studies (including 2026 patients). Live birth was found to be more likely in women replete in vitamin D when compared to women with deficient or insufficient vitamin D status (OR 1.33 [1.08-1.65]). Five studies (including 1700 patients) found that women replete in vitamin D were more likely to achieve a positive pregnancy test than women deficient or insufficient in vitamin D (OR 1.34 ([1.04-1.73]). All 11 of the included studies (including 2700 patients) reported clinical pregnancy as an outcome. Clinical pregnancy was found to be more likely in women replete in vitamin D (OR 1.46 [1.05-2.02]). Six studies (including 1635 patients) reported miscarriage by vitamin D concentrations. There was no association found between miscarriage and vitamin D concentrations (OR 1.12 [0.81-1.54]. The included studies scored well on the Newcastle-Ottawa quality assessment scale. LIMITATIONS REASONS FOR CAUTION: Although strict inclusion criteria were used in the conduct of the systematic review, the included studies are heterogeneous in population characteristics and fertility treatment protocols. WIDER IMPLICATIONS OF THE FINDINGS: The findings of this systematic review show that there is an association between vitamin D status and reproductive treatment outcomes achieved in women undergoing ART. Our results show that vitamin D deficiency and insufficiency could be important conditions to treat in women considering ARTs. A randomized controlled trial to investigate the benefits of vitamin D deficiency treatment should be considered to test this hypothesis. STUDY FUNDING/COMPETING INTERESTS: No external funding was either sought or obtained for this study. The authors have no competing interests to declare. REGISTRATION NUMBER: N/A.