[1] Wayne State Univ, Dept Pediat, Detroit, MI 48202 USA
[2] RTI Int, Social Stat & Environm Sci Unit, Res Triangle Pk, NC USA
[3] Brown Univ, Women & Infants Hosp, Dept Pediat, Providence, RI 02908 USA
[4] Stanford Univ, Sch Med, Dept Pediat, Palo Alto, CA 94304 USA
[5] Yale Univ, Dept Pediat, New Haven, CT 06520 USA
[6] Univ Texas Houston, Sch Med, Dept Pediat, Houston, TX USA
[7] Univ Cincinnati, Dept Pediat, Cincinnati, OH USA
[8] RTI Int, Social Stat & Environm Sci Unit, Rockville, MD USA
[9] Eunice Kennedy Shriver Natl Inst Child Hlth & Hum, NIH, Bethesda, MD 20892 USA