1. Department of Obstetrics and Gynecology, Key Laboratory of Obstetric and Gynecologic and Pediatric Disease and Birth Defects of Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu, Sichaun, China
2. Department of Obstetrics and Gynecology, Minerva Hospital for Women and Children, Chengdu, Sichuan, China
3. Department of Obstetrics and Gynecology, Chengdu Second People’s Hospital, Chengdu, Sichuan, China