1. Department of Obstetrics and Gynecology, Qilu Hospital, Cheeloo College of Medicine, Shangdong University, Jinan, Shangdong 250012, China
2. Department of Obstetrics and Gynecology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230001, China
3. Department of Echocardiography, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230001, China
4. Department of Obstetrics and Gynecology, Jinan Maternity and Child Care Hospital, Jinan, Shandong 250001, China