Inclusion Criteria:  Age ≥18 to ≤ 44 years at enrolment  Planned stimulation in a fixed or flexible GnRH antagonist protocol Planned use of follitropin delta for ovarian stimulation as per SmPC Planned IVF or ICSI treatment with ejaculated or cryopreserved male germ cells, autologous or heterologous, with or without planned genetic testing of the oocytes or embryos Planned preservation of MII oocytes (fertility preservation) Planned triggering of final oocyte maturation with hCG or a GnRH agonist Willingness and consent to participate  Exclusion Criteria:  Serum AMH within 12 months prior to treatment ≤0.3 ng/ml Most recent serum AMH value before start of stimulation older than 12 months Serum AMH value not determined in Roche Elecsys immunoassays Pre-treatment with a combined oral contraceptive "pill" consisting of ethinyl estradiol and a synthetic progestogen