1. Department of Obstetrics and Gynecology, Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong, China (mainland)
2. Department of Obstetrics and Gynecology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China (mainland)
3. Department of Obstetrics and Gynecology, Guangzhou Huadu District Maternal and Child Health Hospital, Guangzhou, Guangdong, China (mainland)
4. Department of Obstetrics and Gynecology, Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People’s Hospital, Guangzhou, Guangdong, China (mainland)
5. Department of Obstetrics and Gynecology, Northwest Women’s and Children’s Hospital, Xian, Shaanxi, China (mainland)
6. Department of Obstetrics and Gynecology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China (mainland)
7. Department of Obstetrics and Gynecology, First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henen, China (mainland)
8. Department of Obstetrics and Gynecology, Peking University Third Hospital, Beijing, China (mainland)
9. Department of Obstetrics and Gynecology, First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang, China (mainland)
10. Department of Obstetrics and Gynecology, First Affiliated Hospital of Chongqing Medical University, Chongqing, China (mainland)
11. Department of Obstetrics and Gynecology, Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong, China (mainland)
12. Institute of Reproductive and Child Health, National Health Commission Key Laboratory of Reproductive Health, Peking University Health Science Center, Beijing, China (mainland)