Risk Factors of Preterm Birth Born in Hospital：a Prospective Multicenter Case-control Study

Obstetrics and Gynecology Hospital of Fudan University, Shanghai

Songjiang Maternity & Child Health Hospital of Shanghai, Shanghai

Jiangsu Province Hospital, Nanjing

Changzhou Maternal and Child Health Care Hospital, Changzhou

Binzhou Medical University Hospital, Binzhou

Affiliated Hospital of Qingdao University, Qingdao

Qingdao Jimo People's Hospital, Qingdao

Jining NO.1 People's Hospital, Jining

Yueqing Hospital Affiliated to Wenzhou Medical University, Wenzhou

Xiamen Maternal and Child Health Care Hospital, Xiamen

The First Affiliated Hospital of Zhengzhou University, Zhengzhou

The Second Affiliated Hospital of Guangzhou Medical University, Guangzhou

The Maternal and Child Health Hospital of Hainan Province, Haikou

The First People's Hospital of Yinchuan, Yingchuan

Tongxin County People's Hospital, Wuzhong