[1] Univ Calif Irvine, Dept Obstet & Gynecol, Div Maternal Fetal Med, Orange, CA 92717 USA
[2] Univ Calif Los Angeles, Dept Obstet & Gynecol, Div Maternal Fetal Med, 10833 LeConte Ave, Los Angeles, CA 90095 USA
[3] Univ Calif Los Angeles, Dept Biomath, Los Angeles, CA USA
[4] Univ Calif Los Angeles, Dept Anesthesia, Los Angeles, CA USA
[5] Univ Calif Los Angeles, Dept Intervent Radiol, Los Angeles, CA USA