1. Department of Gynecology and Obstetrics The First Affiliated Hospital of Xi’an Jiaotong University Xi’an China
2. Department of Gynecology and Obstetrics The First Affiliated Hospital of Xi’an Medical University Xi’an China
3. Department of Obstetrics Baoji Maternal and Children Health Hospital Baoji China
4. Department of Gynecology and Obstetrics Tangdu Hospital, Medical University of the Air Force Xi’an China