Department of Gynaecology and Obstetrics;
General Hospital of Shenyang Military Region;
Shenyang 110016;
Liaoning Province;
China;
Department of Gynaecology and Obstetrics;
the 202 Hospital of Chinese PLA;
Shenyang 110003;
Liaoning Province;
China;
Shenyang Women and Children Health Center;
Shenyang 110014;
Liaoning Province;
China;