1. Graduate School, Tianjin Medical University, Tianjin City 300070, China
2. The No. 2 Department of Ultrasound, Binzhou No. 2 People’s Hospital, Binzhou, Shandong Province 256800, China
3. Maternal and Child Health Planning Service Center of Zhanhua, Binzhou, Shandong Province 256800, China
4. Department of Pelvic Floor Disease Rehabilitation and Treatment, Binzhou No. 2 People’s Hospital, Binzhou, Shandong Province 256800, China
5. Department of Medical Imaging, Cangzhou Central Hospital, Cangzhou Teaching Hospital of Tianjin Medical University, Cangzhou, Hebei Province 061001, China