[1] Hosp Infantil Mexico Dr Federico Gomez, Clin Epidemiol Unit, Mexico City, DF, Mexico
[2] Univ Nacl Autonoma Mexico, Sch Med, Mexico City, DF, Mexico
[3] Inst Mexicano Seguro Social, Unit Epidemiol Res & Hlth Serv, Cuernavaca, Morelos, Mexico
[4] Inst Nacl Salud Publ, Ctr Invest Nutr & Salud, Cuernavaca, Morelos, Mexico
[5] Inst Mexicano Seguro Social, Unit Med Res Clin Epidemiol, Ctr Med Nacl Siglo 21, Mexico City, DF, Mexico
[6] Inst Nacl Perinatol, Dept Nutr, Res Community Intervent, Mexico City, DF, Mexico
[7] Inst Nacl Salud Publ, Res Ctr Populat Hlth, Cuernavaca, Morelos, Mexico