It is basically a replacement for the luteinizing hormone (LH) surge whose effects include final maturation in natural menstrual cycles.
In cycles followed by oocyte donation, use of GnRH agonists instead of hCG decreases the risk of ovarian hyperstimulation syndrome with no evidence of a difference in live birth rate.
[3] In ovulation induction, using clomifene for intended conception by sexual intercourse, however, triggering oocyte release has been shown to decrease pregnancy chances compared to frequent monitoring with LH surge tests.
A Cochrane review estimated that using GnRH agonist instead of hCG in IVF decreases the risk of mild, moderate or severe OHSS with an odds ratio of approximately 0.15.
A Cochrane review of autologous oocyte transfers estimated that GnRH agonist, compared to hCG, gives an odds ratio of pregnancy of approximately 0.47.