1. Department of Obstetrics and Gynecology, Academic Hospital Cologne Weyertal University of Cologne, University Witten-Herdecke, Cologne, Germany
2. Department of Obstetrics and Gynecology, Marien-Hospital Witten, University Witten-Herdecke, Witten, Germany
3. Department of Obstetrics and Gynecology, Academic Hospital Cologne Weyertal University of Cologne, Cologne, Germany