Is it useful to continue administration of gonadotropin releasing hormone (GnRH) agonist after embryo transfer?

INTERVENTION: The number of patients included in both groups was chosen based upon a special statistical calculation which makes the outcome of the study meaningful. After the pre‐calculated number is reached the study is declared finished and we will send data to a statistician to find out of administration of GnRHa in the luteal phase is useful and effective and accordingly we may advise patients to take or not take this medicine after embryo transfer routinely. Participants are randomised to two arms: 1. GnRHa is injected in luteal phase plus the usual luteal phase support 2. The usual luteal phase support only CONDITION: Infertility treated by ICSI ; Pregnancy and Childbirth ; In vitro fertilization PRIMARY OUTCOME: Clinical pregnancy rate, which is measured by BhCG assay 2 weeks after embryo transfer followed by ultrasound at 6?7 weeks to detect fetal echoes and pulsation SECONDARY OUTCOME: Ongoing pregnancy rate, which is diagnosed by ultrasound examination at 20?24 weeks pregnancy to document a viable pregnancy at this point INCLUSION CRITERIA: Women under 40 years old undergoing intracytoplasmic sperm injection (ICSI) in the first or second trial and using the long GnRHa protocol