PPOS (Progestin Primed Ovarian Stimulation) and Corifollitropin Alfa (CFA) Cross-over Study

Prescreening: Clarification: Pre-screening might be performed to identify women with AFC \> 5 and AMH \> 1.1 ng/ml (Bologna criteria, AFC and AMH values are valid for one year). Inclusion criteria for: * Group 1: indication for oocyte cryopreservation * Group 2: indication for IVF/ICSI and PGT-A Inclusion criteria for both groups: * First ovarian stimulation cycle * Aged ≥ 18 and \< 41 years old at the time of first OPU Exclusion Criteria: * contra-indication for ovarian stimulation * expected poor ovarian response (Bologna Criteria) * PCOS patients * refusal to fill out questionnaires before, during and after treatment * simultaneous participation in another clinical study * untreated and uncontrolled thyroid dysfunction; * current use of oral contraceptives, anti-psychotics, anti-epileptics or chemotherapy; * pregnant or breastfeeding women. A woman is considered of childbearing potential (WOCBP), i.e. fertile, following menarche and until becoming postmenopausal unless permanently sterile. Permanent sterilization methods include hysterectomy, bilateral salpingectomy and bilateral oophorectomy. A postmenopausal state is defined as no menses for 12 months without an alternative medical cause.