Comparison of Blood Flow in the Arteriae Uterinae in Ovarian Stimulation Cycles

To evaluate the influence of ovarian stimulation on the blood flow in the arteriae uterinae as well as whether there is an influence of the type of endometrial preparation for FET with either hormonal replacement therapy or natural cycle on the blood flow of the arteria uterina left / right

Inclusion criteria

• Patients who undergo ovarian stimulation in a Gonadotropin-Releasing-Hormone (GnRH)-antagonist protocol for IVF / ICSI
• Patients who have vitrified embryo(s)
• Preparation for FET either in HRT or NC cycle

Exclusion criteria

• Poor responder according to Bologna criteria (Ferraretti et al.) as follows:
• At least two of the following three features must be present:
• (i) Advanced maternal age (≥40 years) or any other risk factor for poor ovarian reserve (POR);
• (ii) A previous POR (≤3 oocytes with a conventional stimulation protocol);
• (iii) An abnormal ovarian reserve test (i.e. antral follicle count (AFC) 5-7 follicles or anti-mullerian hormone (AMH) 0.5 -1.1 ng/ml).
• Uterine surgery for removal of fibroids (hysteroscopic, laparoscopic) or removal of uterine septum
• Endometriosis
• Asherman-Syndrome
• Previous cytotoxic treatment
• Previous radiation of the uterus / adnexal region
• Known hypertension
• Intake of Aspirin or similar medication which might influence the blood flow
• Status after tubal ligation
• Status after surgery in the adnexal region on 1 side