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1 School of Public Health, Chongqing Medical University, Chongqing 400016, China;
2 The State Key Laboratory of Ultrasound in Medicine and Engineering, Chongqing Medical University, Chongqing 400016, China;
3 Department of Health Management Center, Nanchong Central Hospital, North Sichuan Medical University, Nanchong 637001,China;
4 Department of Obstetrics and Gynecology, Nanchong Central Hospital, North Sichuan Medical University, Nanchong 637001, China |
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