The Role of Vitamin D Supplementation in Improving Endometrial Receptivity and Live Birth Rates in Women Undergoing Frozen Embryo Transfer in Baghdad, Iraq

Background: In Middle Eastern populations, the prevalence of vitamin D deficiency is high; this deficiency has the potential to influence reproductive outcomes. This study aimed to determine the efficacy of vitamin D supplementation on endometrial receptivity and live birth rates among women undergoing frozen embryo transfer (FET) in Baghdad, Iraq . Methods: A randomized controlled trial was conducted at a private Center in Baghdad and run from January 2022 to December 2023. Two hundred forty women who were vitamin D deficient (vitamin D levels: <30 ng/mL) and scheduled for frozen embryo transfer (FET). Women were randomized (1:1) to receive either vitamin D3 supplementation (4000 IU per day) or placebo for 12 weeks prior to the FET. The primary outcomes were endometrial thickness, implantation rates, clinical pregnancy rates, and live birth rates . Results: The group who received vitamin D supplementation had a significantly higher mean endometrial thickness (10.2±1.4 mm (vitamin D) vs 8.7±1.2 mm (placebo), p<0.001), implantation rates (42.5% (vitamin D) vs 28.3% (placebo), p<0.01), clinical pregnancy rates (58.3% (vitamin D) vs 38.3% (placebo), p<0.001), and live birth rates (51.7% (vitamin D) vs 30.0% (placebo), p<0.001). Additionally, vitamin D levels improved significantly for the vitamin D group (18.4±5.2 at the beginning of the trial to 45.6±8.3 after supplementation, p<0.001) . Conclusion: Vitamin D supplementation significantly improved endometrial receptivity markers and reproductive outcomes among vitamin D deficient women undergoing frozen embryo transfer in Baghdad, indicating possible therapeutic implications among this population.