1. Department of Obstetrics and Gynecology, University of Bochum, Bochum, Germany; Universitätsfrauenklinik Bochum, Knappschaftskrankenhaus, In der Schornau 23-25, 44982 Bochum, Germany
2. Department of Obstetrics and Gynecology, University of Bochum, Bochum, Germany