1 Nanjing University Medical School, Nanjing, 210008, China.
2 Department of Obstetrics and Gynecology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, 210008, China.
3 Department of Obstetrics and Gynecology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, 210008, China. yalihu@nju.edu.cn.