1. Department of Obstrics and Gynecology, Ruhr-Universität Bochum, Bochum, Germany
2. Department of Obstrics and Gynecology, Ruhr-Universität Bochum, Bochum, Germany; Universitätsfrauenklinik Bochum, Knappschaftskrankenhaus, In der Schornau 23 25, D-44892 Bochum, Germany