The aim of this study is to assess the effect of vitamin D supplementation on vaginal / endometrial biomarkers and endometrial receptivity in women with fertility problems.~Women will have vaginal swab and endometrial biopsy twice. The first endometrial biopsy is performed using a Pipelle sampler 7 days after luteinizing hormone surge (LH+7) at baseline and the attachment rate of the trophoblast spheroid onto the isolated endometrial epithelial cells will be assessed to assess endometrial receptivity at baseline. Implantation biomarkers will be checked.~They will take Vitamin D 50,000 IU once per week for 4 weeks, followed by 50,000 IU once every 2 weeks for 4 weeks. After 8 weeks of Vitamin D, a second vaginal swab and endometrial biopsy using a Pipelle sampler by standard technique will be collected from the patients 7 days after luteinizing hormone surge (LH+7) and the endometrial receptivity will be compared.~The laboratory staff will not know whether the patient is taking any vitamin D when performing the trophoblast spheroid attachment assay/ biomarkers.
This is a prospective study comparing vaginal and endometrial biomarkers and the trophoblast spheroid attachment rate in women with fertility problems before and after taking Vitamin D for 8 weeks.