Effect of vitamin D insufficiency treatment on fertility outcomes in frozen-thawed embryo transfer cycles: A randomized clinical trial

Background: Frozen- thawed embryo transfer is an essential part of ART treatment and outcomes of this procedure are associated with several clinical factors. Several studies have showed an increase level of IVF outcomes in women with sufficient vitamin D. Objective: whether treatment of vitamin D insufficiency can improve pregnancy rates in frozen-thawed embryo transfer cycles. Materials and Methods: This is an interventional, randomized clinical trial. Serum 25-(OH) vitamin D level of 128 women who had undergone IVF/ICSI with cryopreservation of embryos was checked. One hundred fourteen infertile women with insufficient serum vitamin D (less than 30 ng/ml) were included in the study. Fifty seven women were treated with supplementary vitamin D, 50000 IU weekly, for 6-8 weeks and fifty seven women were received no supplementation. One hundred six women completed frozen thawed embryo transfer cycles and included in the final analysis. Primary and secondary outcomes were chemical and clinical pregnancy respectively. Results: Our study did not show any significant difference between vitamin D insufficient and treated women in term of chemical (29.40% vs. 29.10% respectively, p=1.00) or clinical (25.50% vs. 21.80% respectively, p=0.81) pregnancy rates. Conclusion: Vitamin D insufficiency treatment is not associated with higher pregnancy rate in frozen-thawed embryo transfer cycles.