1. Department of Obstetrics and Gynecology, the First Clinical Medical College of Jinan University, Guangzhou, Guangdong 510632, China
2. Center for Reproductive Medicine, the Affiliated Hospital of Youjiang Medical University for Nationalities, Baise, Guangxi 533000, China
3. Department of Epidemiology, School of Medicine, Jinan University, Guangzhou, Guangdong 510632, China
4. Guangdong Women and Children Hospital, Guangzhou, Guangdong 510000, China