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Contributors Drs TW and VW contributed to the design, acquisition of data, analysis, interpretation of data, drafting and review of final article. Dr SI contributed to the design, interpretation of data, drafting, and review of final article.
Competing interests None.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement There were some regional variations in practice, but little difference in terms of the institutional practice of Level 1, 2, or 3 units (data available on request).