[1] Kings Coll London, Inst Women & Childrens Hlth, London, England
[2] Natl & Kapodistrian Univ Athens, Dept Hyg Epidemiol & Med Stat, Athens, Greece
[3] North Middlesex Univ Hosp NHS Trust, London, England
[4] Monash Univ, Melbourne, Vic, Australia
[5] Kings Coll London, Dept Women & Childrens Hlth, London, England
[6] Michigan State Univ, Coll Human Med, E Lansing, MI USA
[7] Univ Edinburgh, MRC Ctr Reprod Hlth, Edinburgh, Scotland
[8] Botswana Harvard AIDS Inst Partnership, Gaborone, Botswana
[9] Univ British Columbia, Dept Obstet & Gynaecol, Vancouver, BC, Canada
[10] Univ Oxford, Nuffield Dept Womens & Reprod Hlth, Oxford, England