IRCT2013060913605N1 IRCT 2013-08-18 Avicenna Infertility Clinic The effect of intrauterine injection of human chorionic gonadotropin (hCG) before embryo transfer on the implantation and pregnancy rates in the intracytoplasmic sperm injection (ICSI) Assessment of the effect of intrauterine injection of human chorionic gonadotropin (hCG) before embryo transfer on the implantation and pregnancy rates in the intracytoplasmic sperm injection (ICSI) method among patients who referred to Avicenna Infertility Clinic during 2013-2014. 2013-07-06 anticipated 121 Complete https://irct.ir/trial/13421 interventional Randomization: Randomized, Blinding: Double blinded, Placebo: Used, Assignment: Parallel, Purpose: Treatment, Other design features: Explanation regarding blinding of the study: It is evident that researcher is aware of the intervention but who performs the intervention is unaware and is not from research group. Moreover, according to informed consent, participants should be informed that may receive a certain drug but they are not aware of their group. All steps of the study are similar for both groups except that controls receive only culture media instead of hCG plus culture media in the treatment group; neither the patient nor the operator is aware of the content of the instillation. It seems there is no problem regarding the blindness of the study. 2-3 Infertility. Intervention 1: Intrauterine injection of hCG and embryo transfer in the treatment group: immediately before embryo transfer, 500 IU of hCG dissolved in 40 microliter culture media is instilled into the uterine cavity using an insemination catheter. After that, embryos are transferred into the uterine cavity. Intervention 2: Intrauterine injection of placebo and embryo transfer in the control group: immediately before embryo transfer only 40 microliter culture media is instilled into the uterine cavity using an insemination catheter. After that, embryos are transferred into the uterine cavity.