Affiliation: | 1. Department of Obstetrics and Gynecology, Peking University First Hospital, Beijing 100034, China;2. Department of Obstetrics and Gynecology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China;3. Department of Obstetrics and Gynecology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA |