作者单位:Stanford Univ, Dept Obstet & Gynecol, Div Maternal Fetal Med & Obstet, Stanford, CA 94305 USA[1]Stanford Univ, Dept Pediat, Div Med Genet, Stanford, CA 94305 USA[2]Stanford Univ, Dept Bioengn, Stanford, CA 94305 USA[3]Stanford Univ, Dept Pediat, Sch Med, Div Neonatal & Dev Med, Stanford, CA 94305 USA[4]