Human chorionic gonadotropin (hCG) is commonly used for final oocyte maturation in ‘‘in vitro fertilization’’ (IVF)-treatment cycles, however, the main important risk is development of severe ovarian hyperstimulation syndrome (OHSS). OHSS can almost be avoided by using gonadotrophin-releasing-hormone agonist for final oocyte maturation in an antagonist protocol. However, primarily this approach lead to a very poor reproductive outcome, despite the use of a standard luteal phase support. The reason seems to be severe luteolysis. Obviously, luteolysis post-gonadotropin-releasing-hormone-agonist (post-GnRH-a) trigger is individual specific, and not all patients will develop a complete luteolysis, as expected previously. Luteolysis can been reverted by the administration of hCG. Unprotected intercourse around the time of ovulation induction and oocyte retrieval can lead to a spontaneous conception in IVF treatment and, endogenous hCG, produced by the trophoblast, will rescue the corpora lutea. Therefore, one should not rely on complete luteolysis after GnRH-a triggering and, especially patients for egg donation and pre-implantation-genetic diagnosis for single gene disorder, have to be counselled to avoid unprotected intercourse.