How vitamin D level influences in vitro fertilization outcomes: results of a systematic review and meta-analysis

Objective: To investigate the impact of serum vitamin D level on in vitro fertilization (IVF) outcomes.Design: Systematic review and meta-analysis. Setting: Not applicable.Patients: Infertile women undergoing conventional IVF or intracytoplasmic sperm injection (ICSI).Interventions: Systematic search of PubMed, MEDLINE, EMBASE, Global Health, The Cochrane Library, Health Technology Assessment Database, and Web of Science from inception until July 2019 with cross-checking of references from relevant articles in English. Vitamin D levels were categorized into three groups: deficient (<20 ng/mL), insufficient (20-30 ng/mL), and replete (>30 ng/mL). Before starting the data extraction, we registered the review protocol in PROSPERO (CRD42019134258).Main Outcome Measures: We consider clinical pregnancy rate (CPR), live birth rate (LBR), and/or ongoing pregnancy rate (OPR) as primary outcomes. Likewise, the miscarriage rate was considered as a secondary outcome.Results: Primary analysis showed thatwomen with a replete level of vitamin D had higher CPR and LBR/OPR compared to those with a deficient of insufficient level of vitaminD. However, sensitivity analysis led to non-significant differences between the comparators for CPR (odds ratio 0.71,95% confidence interval 0.47-1.08, I-2 = 61%) and OPR/LBR(odds ratio 0.78,95% confidence interval 0.56-1.08], I-2 = 61%). Also, for miscarriage a statistically different rate was not reached.Conclusion: Serum vitamin D levels do not influence IVF outcomes in terms of CPR, LBR/OPR, and miscarriage rate. Future large cohort studies are warranted to determine whether the threshold of vitamin D affects reproductive outcomes. Currently, there is a lack of consensus between the appropriate vitamin D threshold to predict reproductive outcomes compared to the one established for bone health. (C) 2020 by American Society for Reproductive Medicine.y