[1] Med Univ Innsbruck, Inst Hlth Econ, Innsbruck, Austria
[2] Univ Med Ctr Utrecht, Julius Ctr Hlth Sci & Primary Care, Utrecht, Netherlands
[3] Univ Cambridge, MRC Biostat Unit, Cambridge, England
[4] Univ Cambridge, Dept Publ Hlth & Primary Care, Cambridge, England
[5] Univ Cambridge, Heart & Lung Res Inst, Cambridge, England
[6] Univ Med Ctr Utrecht, Div Women & Baby, Birth Ctr Wilhelmina Children Hosp, Dept Obstet, Utrecht, Netherlands
[7] Imperial Coll London, Sch Publ Hlth, George Inst Global Hlth, London, England
[8] Univ New South Wales, George Inst Global Hlth, Sydney, NSW, Australia
[9] Univ Med Ctr Utrecht, Julius Ctr Hlth Sci & Primary Care, POB 85500, NL-3508 GA Utrecht, Netherlands