1. People's Hospital of Deyang City; Department of Obstetrics and Gynecology; No. 173, Tai Shan North Road Deyang Sichuan China 618000
2. Cheng du Women & Children's Central Hospital; Department of Obstetrics and Gynecology; No. 1617, Riyue Avenue Chengdu Sichuan China 610091
3. West China Second University Hospital, West China Women's and Children's Hospital; Department of Obstetrics and Gynecology; No. 17, Section Three, Ren Min Nan Lu Avenue Chengdu Sichuan China 610041
4. West China Second University Hospital, Sichuan University; Department of Obstetrics and Gynecology; No. 17, Section Three, Ren Min Nan Lu Avenue Chengdu Sichuan China 610041