[1] Univ British Columbia, Dept Pediat, Fac Med, 4480 Oak St, Vancouver, BC V6H 3V4, Canada
[2] Univ British Columbia, Dept Obstet & Gynaecol, Vancouver, BC, Canada
[3] British Columbia Childrens Hosp, Res Inst, Vancouver, BC, Canada
[4] Univ Manitoba, Coll Pharm, Winnipeg, MB, Canada
[5] Univ Rennes, Irset Inst Rech Sante Environm & Travail UMR S 10, INSERM, EHESP, F-35000 Rennes, France
[6] Lady Davis Inst, Jewish Gen Hosp, Ctr Clin Epidemiol, Montreal, PQ, Canada
[7] McGill Univ, Dept Pediat, Fac Med & Hlth Sci, Montreal, PQ, Canada
[8] McGill Univ, Dept Epidemiol Biostat & Occupat Hlth, Montreal, PQ, Canada
[9] Univ British Columbia, Sch Populat & Publ Hlth, Vancouver, BC, Canada