1. Reproductive Medicine Center, Sun Yat-sen Memorial Hospital of Sun Yat-sen University, Guangzhou, Guangdong 510120, China
2. Reproductive Medicine Center, Shenshan Central Hospital, Sun Yat-sen Memorial Hospital of Sun Yat-sen University, Shanwei, Guangdong 516600, China
3. Department of Public Health and Preventive Medicine, School of Medicine, Jinan University, Guangzhou, Guangdong 510632, China