In 187 patients allocated to fresh ET group, ET were performed on the day 2. Embryos were transferred under ultrasound guidance, with a C.C.D. embryo transfer catheter (Laboratory C.C.D., Paris, France). Luteal support with progesterone in oil (Progesterone, Aburaihan Co., Tehran, Iran) 100 mg daily IM was started on the day of oocyte retrieval and continued until the documentation of fetal heart activity on ultrasound.