Introduction Recent studies have addressed the role of micronutrients in fertilization, such as vitamin D. The present study aims to explore the effects of using calcitriol, an active form of vitamin D, on IVF results in women with vitamin D deficiency. Method This double-blinded randomized clinical trial was done on 180 infertile women, undergone IVF treatment. Out of them, 95 were found to have vitamin D deficiency (blood serum 25-dihydroxy vitamin D <30 ng/ml). Fifty one women in experimental group were treated with two 0.25 µg calcitriol pills daily during 4 weeks (discontinued 8 hours prior to the embryo transfer) and 44 subjects to the placebo group (mean vitamin D deficiency 27.5 ±1.8 in case group vs. 27.6±1.8 in control group, P>0.05). Final analysis includes outcomes of chemical and clinical pregnancy was done on 74 women (including 36 in case and 38 in control group). Results Our study showed that in the experimental group, chemical pregnancy success was significantly higher than that in the control group, 31.4 vs. 18.2% (P<0.05). However, there were no significant differences between the 2 groups in reaching the clinical pregnancy stage (25.5% in case group vs. 13.6% in control group) and continuation of pregnancy into week 20 (9.8% in case group vs. 11.6% in control group) (P>0.05). Conclusion Calcitriol administration by improving the implantation process can significantly increase the chances of successful IVF cycle results in infertile women with vitamin D deficiency.

IntroductionVitamin D is associated with many functions of the human reproductive system. Accordingly, it seems that on infertile couples undergoing assisted reproduction technology (ART), treatment outcomes may be affected by the vitamin D. This overview aims to show the effect of vitamin D on infertility treatments outcomes in recent studies by concluding systematic reviews and meta-analyses to achieve a comprehensive result.Methods and analysisThis overview protocol is being reported according to the Preferred Reporting Items for Systematic review and Meta-Analysis Protocols (PRISMA-P) statement and was registered in the International Prospective Register of Systematic Reviews. We will include all peer-reviewed systematic reviews and meta-analyses of randomised controlled trials published from inception until December 2022. PubMed, Web of Science, Cochrane Database of Systematic Reviews, Cochrane Database of Abstracts of Reviews of Effects, Scopus, Cochrane Central Register of Controlled Trials and Embase will be searched from the time of publication of the first articles onwards with a comprehensive search strategy. Endnote V.X7 software (Thomson Reuters, New York, New York, USA) will be used to store and manage records. The results will align with guidelines in the Cochrane Handbook of Systematic Reviews of Interventions and the PRISMA statement.Ethics and disseminationThis overview will be evaluating the effect of vitamin D status and vitamin D supplementing on results of ART in women and men who are undergoing treatment for infertility. The high prevalence of vitamin D deficiency worldwide and its effects on an important issue such as human fertility might be a very influential factor that leads scientists to strongly recommend its use. However, the more critical concern is that there is no definitive agreement in studies on the relationship between vitamin D and an increased chance of better fertility in men and women undergoing infertility treatment.PROSPERO registration numberCRD42021252752.