[1] Wake Forest Univ, Bowman Gray Sch Med, Dept Pediat, Winston Salem, NC 27157 USA
[2] Harvard Univ, Sch Med, Cambridge, MA 02138 USA
[3] Harvard Univ, Sch Publ Hlth, Cambridge, MA 02138 USA
[4] Boston Med Ctr, Dept Pediat, Boston, MA USA
[5] Michigan State Univ, Dept Epidemiol, E Lansing, MI 48824 USA
[6] Brigham & Womens Hosp, Dept Obstet Gynecol & Reprod Biol, Boston, MA 02115 USA
[7] NINDS, Bethesda, MD 20892 USA