We evaluated the association between infant hair-Hg and Gesell schedules (GS).
Longitudinal assessment of prenatal and postnatal Hg exposure during the first 60 months.
We used hair-Hg as a marker of postnatal Hg exposure (inorganic and methyl-Hg from breast milk, and ethyl-Hg from thimerosal) and GS measured at 6, 36, and 60 months.
Hair-Hg at 6 months responded to events related to Hg exposure and breastfeeding. However, most neurodevelopment delays observed at 6 months were overcome with infant growth; at 60 months 87% of children showed adequate GS (>85). Length of lactation and hair-Hg were each significantly correlated with GS, but in opposite ways: length of lactation was positive and significantly correlated with all GS at 60 months; hair-Hg concentrations were negative and significantly correlated with GS at 6 months (r=−0.333; P=0.002) and 60 months (r=−0.803; P=0.010), but not at 36 months. Multiple regression models showed that the GS outcome at 60 months depended on GS at 36 months that in turn was influenced by infants' developmental and Hg exposure variables. GS at 6 months was significantly influenced by prenatal (maternal and infant hair-Hg at birth) and postnatal Hg exposure at 6 months.
Until there is more refined approach to recognize children sensitive to Hg exposure, and in situations of uncertainty (EtHg exposure), the neurodevelopment benefit of breastfeeding should be recommended.
*Fundação Universidade Federal de Rondônia. Porto Velho, RO
†Instituto de Biofísica Carlos Chagas Filho,Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ
‡Universidade de Brasília, Brasília, DF, Brasil
Supported by United Nations Educational, Scientific and Cultural Organization—UNESCO, Ministério da Saúde do Brasil (SC27824/2005/914BRA2000 Decit PRODOC) and The National Research Council of Brazil-CNPq (PNOPG project-55.0882/01-4; PPG7, project-556985/2005-2).
Reprints: José G. Dórea, PhD, C.P.04322, Universidade de Brasília, 70919-970, Brasília, DF, Brazil (e-mail: email@example.com).
Received for publication April 8, 2008; accepted February 15, 2009