[1] Univ Alabama Birmingham, Dept Pediat, Birmingham, AL 35249 USA
[2] RTI Int, Stat & Epidemiol Unit, Res Triangle Pk, NC USA
[3] RTI Int, Stat & Epidemiol Unit, Rockville, MD USA
[4] Univ Iowa, Dept Pediat, Iowa City, IA 52242 USA
[5] Ohio State Univ, Nationwide Childrens Hosp, Dept Pediat, Columbus, OH 43210 USA
[6] Emory Univ, Sch Med, Dept Pediat, Childrens Healthcare Atlanta,Grady Mem Hosp, Atlanta, GA USA
[7] Univ Texas Southwestern Med Ctr Dallas, Dept Pediat, Dallas, TX USA
[8] Brown Univ, Women & Infants Hosp, Dept Pediat, Providence, RI 02908 USA
[9] Stanford Univ, Sch Med, Lucile Packard Childrens Hosp, Div Neonatal & Dev Med,Dept Pediat, Palo Alto, CA 94304 USA
[10] Duke Univ, Dept Pediat, Durham, NC 27706 USA
[11] Univ Rochester, Sch Med & Dent, Rochester, NY USA
[12] Wayne State Univ, Dept Pediat, Detroit, MI 48202 USA
[13] Univ Penn, Childrens Hosp Philadelphia, Dept Pediat, Philadelphia, PA 19104 USA
[14] Case Western Reserve Univ, Rainbow Babies & Childrens Hosp, Dept Pediat, Cleveland, OH 44106 USA
[15] Eunice Kennedy Shriver Natl Inst Child Hlth & Hum, NIH, Bethesda, MD USA
[16] George Mason Univ, Dept Global & Community Hlth, Fairfax, VA 22030 USA