[1] Univ Calif San Francisco, Dept Surg, Div Pediat Surg, San Francisco, CA 94143 USA
[2] Univ Calif San Francisco, Fetal Treatment Ctr, Dept Surg, San Francisco, CA 94143 USA
[3] Calif State Polytech Univ Pomona, Dept Anim & Vet Sci, Pomona, CA 91768 USA
[4] Hosp Univ La Paz, Dept Pediat Surg, Madrid, Spain
[5] Univ Calif Berkeley, Dept Bioengn, Berkeley, CA 94720 USA
[6] Univ Calif San Francisco, Dept Neurol Surg, Brain & Spinal Injury Ctr, San Francisco, CA USA