Inclusion Criteria:  Infertile women candidates for frozen embryo transfer Age 20-40 years Body Mass Index under than 30 Kg/m2 Having at least three good quality embryos  Exclusion Criteria:  Women with hematologic and autoimmune disorders Couples with chromosomal and genetic abnormalities Women with uterine anomalies Women with uterine and ovaries surgical history Women with endometriosis and adenomyosis Women with hydrosalpinx Women with uterine fibroids Women with history of recurrent abortion or recurrent implantation failure Severe male factor infertility (azoospermia) Embryo donation cycle Endometrial thickness less than 8 millimeter on the day of embryo transfer