[1] Johns Hopkins Univ, Sch Med, Dept Gynecol & Obstet, Integrated Res Ctr Fetal Med, Baltimore, MD 21205 USA
[2] Johns Hopkins Univ, Sch Med, Dept Pediat, Baltimore, MD 21205 USA
[3] Univ Penn, Sch Med, Dept Obstet & Gynecol, Philadelphia, PA 19104 USA
[4] Johns Hopkins Univ, Sch Med, Dept Neurol, Baltimore, MD 21205 USA