[1] Dalhousie Univ, Dept Obstet & Gynaecol, Perinatal Epidemiol Res Unit, Halifax, NS, Canada
[2] Dalhousie Univ, Dept Pediat, Perinatal Epidemiol Res Unit, Halifax, NS, Canada
[3] Dalhousie Univ, Dept Family Med, Halifax, NS, Canada
[4] Dalhousie Univ, Sch Hlth & Human Performance, Halifax, NS, Canada
[5] IWK Hlth Ctr, Halifax, NS, Canada