1 Department of Obstetrics and Gynecology, West China Second Hospital, Sichuan University, Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, Chengdu, Sichuan, 610041, China.
2 Department of Obstetrics and Gynecology, West China Second Hospital, Sichuan University, Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, Chengdu, Sichuan, 610041, China. Electronic address: zhengaiwestchina@163.com.