Foshan Fetal Medicine Research Institute, Affiliated Foshan Women and Children Hospital, Southern Medical University, Foshan, Guangdong, China. Department of Obstetrics, Affiliated Foshan Women and Children Hospital, Southern Medical University, Foshan, Guangdong, China. Australian Centre for Health Services Innovation and Centre for Healthcare Transformation, School of Public Health & Social Work, Faculty of Health, Queensland University of Technology, Australia. Department of Epidemiology and Biostatistics, School of Public Health, Anhui Medical University, Hefei, Anhui, China. Department of Library, the First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China. Department of Health Management and Policy, School of Public Health, Capital Medical University, Beijing, China. School of Medicine, Foshan University, Foshan, Guangdong, China.