On the other hand, the women in the study group (group 2, n=50) will undergo endometrial biopsies with one-week intervals at the luteal phase of nontransfer cycle. Endometrial biopsy will performe with biopsy catheter (Pipelle; de Cornier, Prodimed, Neuilly-en-Thelle, France). The catheter will be passed through the cervical os and will rotate in uterine cavity and apply 3-4 times after withdrawing the piston.