Ovulation trigger is needed in in vitro fertilization (IVF) to get mature eggs. Routinely, human chorionic gonadotropin (hCG) is used for that purpose given its similarity to the natural hormone that does this job in a natural cycle (luteinizing hormone, LH). In a natural cycle another hormone takes part in the process (follicle stimulating hormone, FSH). To induce a natural-like ovulation surge that includes LH and FSH , gonadotropin releasing hormone (GnRH) agonist can be given.