1. Institute for Prenatal Health; Bahnhofstr. 4; 38300; Wolfenbüttel; Germany
2. Klinikum Oldenburg gGmbH; Klinik für Allgemein- und Viszeralchirurgie; Rahel-Straus-Str. 10; 26133; Oldenburg; Germany
3. Department of Medical Statistics and Biometry; Medical University of Hannover; Carl-Neuberg-Str. 1; 30625; Hannover; Germany
4. Department for Obstetrics and Gynecology; Medical University of Hannover; Carl-Neuberg-Str. 1; 30625; Hannover; Germany