1,200
Participants
Start Date
January 30, 2019
Primary Completion Date
January 29, 2020
Study Completion Date
January 29, 2020
no interventions
no interventions because of an observational study
Qi Feng, Beijing
Peking University First Hospital
OTHER
Peking University People's Hospital
OTHER
Peking University Third Hospital
OTHER
Tianjin Central Hospital of Gynecology Obstetrics
OTHER
Peking Union Medical College Hospital
OTHER
Beijing Children's Hospital
OTHER
Beijing Friendship Hospital
OTHER
Shanxi Provincial Maternity and Children's Hospital
OTHER
The Second Hospital of Hebei Medical University
OTHER
Handan Central Hospital
OTHER
Xingtai People's Hospital
OTHER
Tianjin Medical University General Hospital
OTHER
The Affiliated Hospital of Inner Mongolia Medical University
OTHER
Children's Hospital of Hebei Province
OTHER
Tianjin First Central Hospital
OTHER
Chifeng Municipal Hospital
OTHER
Tianjin Medical University Second Hospital
OTHER
PLA Rocket Force Characteristic Medical Center
OTHER
Peking University
OTHER