[1] London Sch Hyg & Trop Med, Fac Publ Hlth & Policy, London, England
[2] London Sch Hyg & Trop Med, Fac Epidemiol & Populat Hlth, London, England
[3] Imperial Coll London, Inst Reprod & Dev Biol, London, England
[4] UCL, Inst Hlth Informat, London, England
[5] Univ Oxford, Nuffield Dept Populat Hlth, Natl Perinatal Epidemiol Unit, Oxford, England
[6] Univ Liverpool, Sch Hlth Sci, Liverpool, England
[7] Univ Edinburgh, Usher Inst, Ctr Global Hlth, Edinburgh, Scotland
[8] Leibniz Inst Prevent Res & Epidemiol, Bremen, Germany
[9] Univ Bremen, Hlth Sci, Bremen, Germany
[10] UCL, Inst Hlth Informat, London NW1 2DA, England