[1] Univ Montreal, Dept Social & Prevent Med, Montreal, PQ H3N 1X9, Canada
[2] St Justine Hosp Res Ctr, Montreal, PQ H3T 1C5, Canada
[3] Ctr Rech CHUM CRCHUM, Montreal, PQ H2X 0A9, Canada
[4] Univ Montreal, Dept Obstet & Gynecol, Montreal, PQ H3N 1X9, Canada
[5] St Justine Hosp, Dept Obstet & Gynecol, Montreal, PQ H3T 1C5, Canada
[6] McGill Univ, Hlth Ctr, Div Clin Epidemiol, Montreal, PQ H4A 3J1, Canada
[7] Univ Sherbrooke, Ctr Rech CHUS, Dept Obstet & Gynecol, Sherbrooke, PQ J1H 5N4, Canada
[8] St Marys Hosp, Dept Obstet & Gynecol, Montreal, PQ H3T 1M5, Canada
[9] St Justine Hop, Dept Pediat, Div Pediat Intens Care, Montreal, PQ H3T 1C5, Canada
[10] Univ Montreal, St Justine Hosp, Dept Pediat, Montreal, PQ H3T 1C5, Canada
[11] Univ Montreal, Dept Microbiol Infectiol & Immunol, Montreal, PQ H2X 0A9, Canada