[1] Childrens Hosp Philadelphia, Dept Radiol, 3401 Civ Ctr Blvd, Philadelphia, PA 19104 USA
[2] Childrens Hosp Philadelphia, Dept Pediat, Div Endocrinol & Diabet, 3401 Civ Ctr Blvd, Philadelphia, PA 19104 USA
[3] Childrens Hosp Philadelphia, Dept Pediat, Div Gastroenterol Hepatol & Nutr, 3401 Civ Ctr Blvd, Philadelphia, PA 19104 USA
[4] Univ Penn, Perelman Sch Med, 3400 Civ Ctr Blvd, Philadelphia, PA 19104 USA
[5] NIEHS, Epidemiol Branch, NIH, Res Triangle Pk, NC 27709 USA
[6] NIEHS, Biostat & Computat Biol Branch, NIH, POB 12233, Res Triangle Pk, NC 27709 USA
[7] Vanderbilt Univ, Med Ctr, Dept Pediat, Nashville, TN 37232 USA