[1] Childrens Hosp Boston, Dept Neurol, Boston, MA USA
[2] Harvard Univ, Sch Med, Boston, MA USA
[3] Brigham & Womens Hosp, Dept Obstet Gynecol & Reprod Biol, Boston, MA 02115 USA
[4] Floating Hosp Children, Tufts Med Ctr, Boston, MA 02111 USA
[5] Beth Israel Deaconess Med Ctr, Dept Pathol, Boston, MA 02215 USA
[6] Boston Univ, Div Pediat Neurol, Dept Pediat, Boston Med Ctr, Boston, MA 02215 USA
[7] Wake Forest Univ, Dept Pediat, Winston Salem, NC 27109 USA
[8] Michigan State Univ, Dept Epidemiol, E Lansing, MI 48824 USA