[1] Stanford Univ, Sch Med, Dept Med, 1265 Welch Rd,Room X328, Stanford, CA 94305 USA
[2] Univ Calif Berkeley, Sch Publ Hlth, Div Epidemiol, Berkeley, CA 94720 USA
[3] Univ Calif Berkeley, Sch Publ Hlth, Div Biostat, Berkeley, CA 94720 USA
[4] Univ Calif Berkeley, Sch Publ Hlth, Div Maternal & Child Hlth, Berkeley, CA 94720 USA
[5] Univ Calif, Nutr Policy Inst, Div Agr & Nat Resources, Oakland, CA USA