[1] Univ Calif Los Angeles, Med Ctr, Los Angeles Biomed Res Inst Harbor, Dept Obstet & Gynecol,Perinatal Res Labs, Torrance, CA 90502 USA
[2] Univ Calif Los Angeles, David Geffen Sch Med, Dept Obstet & Gynecol, Los Angeles, CA 90095 USA
[3] Los Angeles Perinatal Assoc, Los Angeles, CA USA
[4] Med Coll Wisconsin, Dept Pediat, Milwaukee, WI 53226 USA