1. Clinic of Gynecology and Obstetrics, Diakonie-Klinikum, Schwaebisch Hall, Germany
2. Practice of Prenatal Medicine, Berlin, Germany
3. Department of Obstetrics, University Clinic, Graz, Austria
4. University Clinic of Obstetrics and Gynecology, Tübingen, Germany
5. Prenatal Medicine and Genetics, Duesseldorf, Germany
6. Department of Obstetrics and Gynecology, Hannover Medical School, Hannover, Germany
7. Clinic of Obstetrics, University Hospital, Zurich, Switzerland