[1] Univ Glasgow, Inst Hlth & Wellbeing, Glasgow, Lanark, Scotland
[2] NHS Natl Serv Scotland, Informat Serv Div, Edinburgh, Midlothian, Scotland
[3] Scottish Govt, ScotXed Unit, Edinburgh, Midlothian, Scotland
[4] Univ Cambridge, Dept Obstet & Gynaecol, Cambridge, England