On day of HCG injection (main follicular diameter of 18 mm) in the 6th, and 7th cycles, women came for follow up and had transvaginal sonographic assessment of their endometrial thickness. Investigators have measured the maximal distance spanning endometrial- myometrial interphase on each endometrial stripe in a sagittal plane in the fundus of the uterus. In addition, Transvaginal Doppler examination was also done on the same visit to evaluate the pulsatility indices of both uterine arteries. When the leading follicle reached 18 mm in diameter, 5000 IU of HCG was prescribed for IM injection.