1. Ocean University of China, Qingdao, Shandong, China
2. Qingdao University Affiliated Qingdao Women and Children’s Hospital, Qingdao, Shandong, China
3. Weifang Maternal and Child Health Hospital, Weifang, Shandong, China
4. Tengzhou Maternal and Child Health Hospital, Tengzhou, Shandong, China
5. Jinan Maternal and Child Health Hospital, Jinan, Shandong, China
6. Linyi Maternal and Child Health Hospital, Linyi, Shandong, China
7. Zaozhuang Maternal and Child Health Hospital, Zaozhuang, Shandong, China
8. Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, China
9. Qingdao Haici Hospital, Qingdao, Shandong, China
10. Shandong Qianfuo Mountain Hospital, Jinan, Shandong, China
11. The Second People’s Hospital of Shandong Province, Jinan, Shandong, China
12. Qingdao Municipal Hospital Group, Qingdao, Shandong, China
13. Qingdao University Affiliated Qingdao Women and Children’s Hospital, No. 217, Liaoyang East Road, North District, Qingdao, Shandong, China