Chengdu Donghua Reproductive Health Research hlstitute, Chengdu 610017, China;
Affiliated Hospital of Sichuan Reproductive Health Research Center, Chengdu 610031, China;
The Family Planning Guidance Station of Meishan Downtown, Meishan 610041, China;
The Hospital for Staffs and Workers of Forest Creation Bureau of Changjiang, Yibin 644002, China;
The Family Planning Guidance Institution of Luzhou, Luozhou, Sichuan 646000, China;
The Family Planning Guidance Station of Pengshan. Pengshan, Sichuan 612700, China;