1. Department of Obstetrics and Gynecology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China (mainland)
2. Department of Obstetrics and Gynecology, Central Hospital of Chancheng, Foshan, Guangdong, China (mainland)
3. Department of Obstetrics and Gynecology, The First People’s Hospital of Shunde, Foshan, Guangdong, China (mainland)
4. Department of Obstetrics and Gynecology, Women and Child Health Hospital, Zhuhai, Guangdong, China (mainland)
5. Department of Obstetrics and Gynecology, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong, China (mainland)
6. Department of Obstetrics and Gynecology, Central Hospital of Panyu, Guangzhou, Guangdong, China (mainland)
7. Department of Obstetrics and Gynecology, Xiaolan People’s Hospital, Zhongshan, Guangdong, China (mainland)
8. Department of Obstetrics and Gynecology, The Hexian Memorial Hospital of Panyu, Guangzhou, Guangdong, China (mainland)
9. Department of Obstetrics and Gynecology, Huadu People’s Hospital, Guangzhou, Guangdong, China (mainland)
10. Department of Obstetrics and Gynecology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong, China (mainland)