1. Department of Obstetrics and Gynecology; Bürgerhospital; Frankfurt Germany
2. Department of Biostatistics, Central Institute of Mental Health; Medical Faculty Mannheim/Heidelberg University; Mannheim Germany
3. Center of Prenatal Diagnosis and Human Genetics; Munich Germany
4. Department of Obstetrics and Gynecology; University of Bonn; Bonn Germany
5. Department of Obstetrics and Gynecology; University of Hannover; Hannover Germany
6. Department of Obstetrics and Gynecology; University of Münster; Münster Germany
7. Department of Obstetrics and Gynecology; Virchow University; Berlin Germany
8. Center of Prenatal Diagnosis and Human Genetics; Berlin Germany
9. Department of Obstetrics and Gynecology; Ludwig-Maximilians-University; Munich Germany
10. Department of Obstetrics and Gynecology; Charite University; Berlin Germany
11. Department of Obstetrics and Gynecology; Friedrich-Alexander University; Erlangen Germany
12. Department of Obstetrics and Gynecology; University of Regensburg; Germany
13. Department of Obstetrics and Gynecology; Schwäbisch-Hall Germany
14. Center of Prenatal Diagnosis and Human Genetics; Düsseldorf Germany