1. Department of OB/GYN, University of Witten Herdecke, Hospital Dormagen, Dormagen, Germany.
2. Department of OB/GYN, University of Witten Herdecke, Marien Hospital Witten, Witten, Germany.
3. Department of OB/GYN, University of Kiel, Kiel, Germany.
4. Department of OB/GYN, Hospital Dormagen, Dormagen, Germany.