On the day 2, the embryos were translated from the old dish to a new dish with fresh media and cultured continuously. In study group, the embryo culture supernatant at the old dish were aspirated by using embryo transfer catheter (COOK-5000, Australia) and injected into the patient's uterine cavity. ET was performed on the third day of embryo culture. Two to three embryos were selected to transfer for each woman. The number of embryos selected for transfer was based on morphologic criteria and some additional factors, such as duration and cause of infertility and age of the patient. Pregnancy was determined by carry out a urine pregnancy test after 14 days of ET. The embryo implantation, the number of gestational sacs, and embryo heart pulsation were determined by TVS in the seventh week of pregnancy. Except the day 2 embryo culture supernatant injection, all of the above-mentioned clinical and laboratory procedures were identical between the study group and control group.