Is the Diurnal Variation in Circulating Levels of Cortisol Reflected in Follicular Fluid of Preovulatory Follicles Close to Ovulation?

Inclusion Criteria: * Indication for IVF / ICSI - treatment * Age ≥ 18 years and ≤ 35 years * Body weight: 19 - 29 kg/m2 * Ovarian reserve parameters in the adequate age - range, determined by Anti-Muellerian-Hormone (AMH) and Antral Follicle Count (AFC) (Shebl 2011, Hamdine 2015) * Regular cycle (25-35 days) Exclusion Criteria: * Age \< 18 years and \> 35 years * Body weight \< 60 kg and \> 90 kg * Ovarian reserve parameters outside the adequate age - range, determined by Anti-Muellerian-Hormone (AMH) and Antral Follicle Count (AFC) (Shebl 2011, Hamdine 2015) * Proven poor responder in preceding IVF-treatment-cycle, according to the Bologna criteria: at least two of the following three features must be present: (i) Advanced maternal age (≥40 years) or any other risk factor for POR (poor ovarian response) (ii) A previous POR (≤3 oocytes with a conventional stimulation protocol) (iii) An abnormal ovarian reserve test (i.e. AFC \< 5-7 follicles or AMH \< 0.5 -1.1 ng/ml) * Two episodes of POR after maximal stimulation are sufficient to define a patient as a poor responder in the absence of advanced maternal age or abnormal ORT * Diagnosis of polycystic ovarian syndrome (PCOS), according to Rotterdam criteria * Endometriosis stage 3 or 4 AFS (American Fertility Society) * Irregular cycle (\< 25 days and \> 35 days) * Treatment with GnRH-analogues during the previous 6 months * Intake of contraceptive pill (OCP) or any hormonal treatment during the last 3 months