1. Department of Gynaecology, People’s Hospital of Rizhao, Rizhao 276826, Shandong, China
2. Department of Radiology, People’s Hospital of Lixia District, Jinan 250013, Shandong, China
3. Department of Postpartum Rehabilitation, Zibo City Maternal and Child Health Care Hospital, Zibo 250031, Shandong, China