Subjects Twenty eight apparently healthy women, fourteen of them with a ultrasonographic homogeneous echo(group 1) and other fourteen with a " triple-line"(group 2) endometrium in the late follicle phase, were involved in our Department for the study between September 2010 and November 2011. The included criteria for both groups of women were ≤40 years of age, with a regular menstrual cycles (25-35 days), without use of an intrauterine devices or oral contraceptive at least 3 months before the study. Exclusion criteria were women with polycystic ovarian syndrome (PCOS), endometriosis, premature ovarian failure (POF) and an abortion within 1 year or a history of pelvic inflammatory disease. The mean age of the women were 31.9±3.7 years ( range, 26-39 years). The mean body mass index was 20.96±2.46 kg/m2 (range, 17.58-26.04 kg/m2).With a regular menstrual cycle (25-35days) and 2-11 years infertile history, all subjects had signed the proper consent forms. The study was approved by our Institutional Ethics committee.