Women with infertility  Inclusion criteria:  The patient suffers from primary or secondary infertility, defined as the inability to conceive despite frequent unprotected sexual intercourse for at least 12 months. The patient has given her written informed consent after detailed information on the study by medical professionals at the Department of Obstetrics and Gynecology of the Medical University of Vienna. The patient is >18 and <40 years old.  Exclusion criteria:  Inflammatoric bowel disease, cardiac insufficiency, chronic kidney disease, any malignant diseases. Polycystic ovary syndrome. There is no "informed consent".  Women with recurrent miscarriage  Inclusion criteria:  The patient suffers from recurrent miscarriage, defined as three or more consecutive miscarriages before the 20th gestation week with the same partner. The patient has given her written informed consent after detailed information on the study by medical professionals at the Department of Obstetrics and Gynecology of the Medical University of Vienna. The patient is >18 and <40 years old.  Exclusion criteria:  Inflammatoric bowel disease, cardiac insufficiency, chronic kidney disease, any malignant diseases. Polycystic ovary syndrome There is no "informed consent".  Healthy controls  Inclusion criteria:  The woman does neither suffer from infertility/sterility nor from recurrent miscarriage and is also otherwise healthy with regular cycles. The patient has given her written informed consent after detailed information on the study by medical professionals at the Department of Obstetrics and Gynecology of the Medical University of Vienna. The patient is >18 and <40 years old.  Exclusion criteria:  Inflammatoric bowel disease, cardiac insufficiency, chronic kidney disease, any malignant diseases. Polycystic ovary syndrome There is no "informed consent".