[1] Drexel Univ, Dept Obstet & Gynecol, Philadelphia, PA 19104 USA
[2] Univ Washington, Dept Obstet & Gynecol, Seattle, WA 98195 USA
[3] Ohio State Univ, Dept Obstet & Gynecol, Med Ctr, Div Maternal Fetal Med, Columbus, OH 43210 USA
[4] Univ Oxford, Nuffield Dept Obstet & Gynaecol, Oxford, England
[5] McGill Univ, Dept Pediat, Fac Med, Montreal, PQ H3A 2T5, Canada
[6] McGill Univ, Fac Med, Dept Epidemiol Biostat & Occupat Hlth, Montreal, PQ H3A 2T5, Canada
[7] Univ Penn, Dept Pediat, Philadelphia, PA 19104 USA
[8] Univ Catolica Pelotas, Postgrad Course Hlth & Behav, Pelotas, RS, Brazil
[9] Eunice Kennedy Shriver Natl Inst Child Hlth & Hum, Perinatol Res Branch, NIH, Dept Hlth & Human Serv, Bethesda, MD USA
[10] Eunice Kennedy Shriver Natl Inst Child Hlth & Hum, Perinatol Res Branch, NIH, Dept Hlth & Human Serv, Detroit, MI USA
[11] Aga Khan Univ, Div Women & Child Hlth, Karachi, Pakistan