1. Department of Obstetrics and Gynecology, Peking Union Medical College Hospital, Chinese Academy of Medical Science, Beijing, China
2. Department of Obstetrics and Gynecology, Beijing Chaoyang Hospital, Affiliated to Capital University of Medical Science, Beijing, China
3. Department of Pulmonary and Critical Care Medicine, Peking Union Medical College Hospital, Chinese Academy of Medical Science, Beijing, China
4. Peking Union Medical College Hospital, Beijing, China