1. Department of Obstetrics and Gynecology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, People’s Republic of China
2. Department of Clinical Laboratory, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, People’s Republic of China
3. Department of Infectious Diseases, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, People’s Republic of China
4. Department of Obstetrics and Gynecology, Tufts University Medical School, Boston, Massachusetts, USA
5. Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, People’s Republic of China