For the control group, as well as for the study group, final oocyte maturation was achieved by administration of either 5.000 IU of hCG or, in case of a risk of ovarian hyperstimulation syndrome (OHSS) (17), with 0.3 mg of GnRH agonist (Triptorelin) as soon as ≥ 3 follicles ≥ 17 mm were present. Here, GNRH1 is linked to ovarian hyperstimulation syndrome.