1. Department of Obstetrics and Gynecology, Asklepios Clinic Barmbek, Hamburg, Germany
2. Department of Obstetrics, Universitätsmedizin Charité, Berlin, Germany
3. Asklepios Pro-Research, Hamburg, Germany
4. Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
5. Department of Obstetrics and Gynecology, Charité University Hospital Berlin, Charitéplatz 1, 10117 Berlin, Germany