Vitamin D and Endometrial Receptivity in Infertile Women

Inclusion Criteria: * Age of women \< 40years old * Normal uterine cavity as demonstrated by pelvic scanning with or without saline infusion sonogram or hysteroscopy * Regular ovulatory cycles They will be divided into three groups: * RIF patients (n=35)- those who have failed to get pregnant after replacing four or more cleavage stage embryos or two or more blastocysts in two consecutive transfers. * RPL patients (n=35)- those who have failed in three pregnancies before 24 weeks of gestation and includes embryonic and fetal losses. * 'Infertile group'(n=35)- infertility except RIF and RPL, e.g. those seeking for preimplantation genetic testing, male factor infertility, unexplained infertility. Exclusion Criteria: * History of any medical condition or medications that may predispose to vitamin D sensitivity, altered vitamin D metabolism and/ or hypercalcemia, including active tuberculosis or current therapy for tuberculosis, sarcoidosis, history of renal/ ureteral stones, parathyroid disease, renal or liver failure or current use of anti-convulsants * Taking vitamin D supplement * Endometrial polyp or fibroid distorting the uterine cavity * Presence of hydrosalpinx not corrected surgically * Refusal to join the study • Discontinuation criteria- * If the woman becomes pregnant during the study * Pelvic inflammatory disease/ uterine perforation after endometrial biopsy * Vitamin D toxicity (hypercalcemia) * Withdrawal by patient