[1] Univ Oulu, Univ Hosp Oulu, Dept Obstet & Gynecol, Aapistie 5,BOX 5000, FI-90014 Oulu, Finland
[2] Univ Oulu, Univ Hosp Oulu, Med Res Ctr, FI-90014 Oulu, Finland
[3] Univ Oulu, Univ Hosp Oulu, PEDEGO Res Unit, FI-90014 Oulu, Finland
[4] Univ Oulu, Univ Hosp Oulu, Ctr Life Course Hlth Res, FI-90014 Oulu, Finland
[5] Univ Oulu, Univ Hosp Oulu, Dept Clin Chem, NordLab Oulu, FI-90014 Oulu, Finland
[6] Imperial Coll London, Inst Reprod & Dev Biol, London W12 ONN, England
[7] Univ Oulu, Univ Hosp Oulu, Fac Med, Ctr Life Course Epidemiol, FI-90014 Oulu, Finland
[8] Imperial Coll London, Sch Publ Hlth, Ctr Environm & Hlth, Dept Epidemiol & Biostat,Med Res Council,Publ Hlt, London W2 1PG, England
[9] Univ Helsinki, Helsinki Univ Hosp, Dept Obstet & Gynecol, FI-00014 Helsinki, Finland
[10] Univ Oulu, Fac Med, FI-90014 Oulu, Finland