1. Fujian Maternity and Child Health Hospital, College of Clinical Medicine for Obstetrics & Gynecology and Pediatrics, Fujian Medical University, Fuzhou, China
2. Fujian Clinical Research Center for Maternal-Fetal Medicine, Fuzhou, China
3. Department of Obstetrics, National Key Obstetric Clinical Specialty Construction Institution of China, Fuzhou, China
4. Department of Ultrasonography, Clinical Medical School of Fujian Medical University, Fujian Provincial Hospital, Fuzhou, China
5. Department of Obstetrics, Fujian Obstetrics and Gynecology Hospital, Fuzhou, China