1. Shandong First Medical University, Jinan, China.
2. Departments of Obstetrics and Gynecology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China.
3. The Affiliated Taian City Central Hospital of Qingdao University, Taian, China.
4. Department of Obstetrics and Gynecology, Shandong Provincial Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China.
5. Department of Ultrasonography, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China.
6. Division of Oral Biotechnology, Center for Dental Medicine, Medical Center–University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
7. Department of Obstetrics and Gynecology, Peking University Shenzhen Hospital, Shenzhen, China.