[1] Univ Wisconsin, Waisman Ctr, Rm 529,1500 Highland Ave, Madison, WI 53705 USA
[2] Univ N Carolina, Gillings Sch Global Publ Hlth, Dept Epidemiol, 135 Dauer Dr, Chapel Hill, NC 27599 USA
[3] Kaiser Permanente, Div Res, 2000 Broadway, Oakland, CA 94612 USA
[4] Univ Colorado, Sch Publ Hlth, Colorado Sch Publ Hlth, Dept Epidemiol, Anschutz Med Campus,13001 E 17th Pl, Aurora, CO 80045 USA
[5] Ctr Dis Control & Prevent, Natl Ctr Birth Defects & Dev Disabil, 1600 Clifton Rd, Atlanta, GA 30329 USA
[6] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Epidemiol, 615 N Wolfe St, Baltimore, MD 21205 USA