[1] Univ Arkansas Med Sci Hosp, Dept Pediat, Coll Med, Arkansas Childrens Hosp Res Inst, Little Rock, AR 72202 USA
[2] Ctr Dis Control & Prevent, Div Birth Defects & Dev Disabil, Natl Ctr Birth Defects & Dev Disabil, Atlanta, GA USA
[3] Texas Dept State Hlth Serv, Birth Defects Epidemiol & Surveillance Branch, Austin, TX USA
[4] Univ N Carolina, Sch Publ Hlth, Dept Epidemiol, Chapel Hill, NC USA
[5] Univ N Carolina, Sch Publ Hlth, Dept Nutr, Chapel Hill, NC 27599 USA
[6] Stanford Univ, Sch Med, Dept Pediat, Div Neonatal & Dev Med, Palo Alto, CA 94304 USA