1School of Public Health, Curtin University, Perth, WA, Australia

2School of Medicine, Shanghai Jiao Tong University, Shanghai, China

3Centre for Midwifery, Child and Family Health, Faculty of Health, University of Technology Sydney, Ultimo, NSW, Australia

4Data Analysis & Surgical Outcomes Unit (DASO), Royal North Shore Hospital, St Leonards, NSW, Australia

5Department of Psychiatry, Westmead Hospital, Wentworthville, NSW, Australia

6Burnet Institute, Melbourne, VIC, Australia

Fenglian Xu, Data Analysis & Surgical Outcomes Unit (DASO), Royal North Shore Hospital, St Leonards, Sydney, NSW 2065, Australia. Email: [email protected]