[1] Univ Oulu, Oulu Univ Hosp, Dept Obstet & Gynaecol, Med Res Ctr Oulu, FI-90029 Oulu, Finland
[2] PEDEGO Res Unit, FI-90029 Oulu, Finland
[3] Univ Oulu, Ctr Life Course Hlth Res, FI-90014 Oulu, Finland
[4] Oulu Univ Hosp, Unit Primary Hlth Care, FI-90220 Oulu, Finland
[5] Univ Oulu, Oulu Univ Hosp, Dept Clin Chem, NordLab Oulu, FI-90220 Oulu, Finland
[6] Med Res Ctr, FI-90220 Oulu, Finland
[7] Natl Inst Hlth & Welf, Dept Children Young People & Families, FI-90101 Oulu, Finland
[8] Imperial Coll London, Sch Publ Hlth, MRC PHE Ctr Environm & Hlth, Dept Epidemiol & Biostat, London W2 1PG, England
[9] Univ Helsinki, Dept Obstet & Gynaecol, FI-00014 Helsinki, Finland
[10] Helsinki Univ Hosp, FI-00014 Helsinki, Finland
[11] Imperial Coll London, Inst Reprod & Dev Biol, Hammersmith Hosp, London W12 0NN, England