1. Department of Obstetrics and Gynecology, Maternal & Child Health Center The First Affiliated Hospital of Xi’an Jiaotong University Xi’an China
2. School of Public Health Xi’an Jiaotong University Health Science Center Xi’an China
3. Shenzhen Health Development Research and Data Management Center Shenzhen China
4. Department of Pediatrics The First Affiliated Hospital of Xi’an Jiaotong University Xi’an China
5. Department of Epidemiology and Biostatistics School of Public Health Xi’an Jiaotong University Health Science Center Xi’an China
6. Department of Public Health and Community Medicine Tufts University School of Medicine Boston Massachusetts USA