1. Department of Gynecology and Obstetrics, University of Schleswig-Holstein, Luebeck, Germany
2. Department of Gynecology and Obstetrics, Technical University of Aachen, Aachen, Germany
3. Praxisklinik für Fertilität, Am Gendarmenmarkt, Berlin, Germany
4. Department of Gynecology and Obstetrics, University of Schleswig-Holstein, Luebeck, Germany,