Main neurodevelopmental study of Seychellois children following in utero exposure to methylmercury from a maternal fish diet: outcome at six months.

Methylmercury (MeHg) is a human neurotoxin to which the developing fetal brain is especially sensitive. The lowest dose of MeHg that impairs neurodevelopment in the human fetus is not known. The Seychelles Child Development Study (SCDS) is testing the hypothesis that fetal MeHg exposure from a maternal diet high in oceanic fish is related to child neurodevelopmental outcomes. Fish is the major protein source in the Republic of Seychelles, where a cohort of 779 mother-infant pairs was enrolled in a prospective longitudinal study. Maternal total hair mercury values during pregnancy were determined by cold vapor atomic absorption and ranged from 0.5 ppm to 26.7 ppm with a median of 5.9 ppm. When the children were 6 1/2 months of age, an examiner blinded to the maternal mercury value performed a neurological examination, the Fagan test of visual recognition memory, and the Denver Developmental Screening Test-Revised (DDST-R). On the DDST-R 2% scored other than normal while 3.4% had an overall neurological score other than normal. The Fagan test of visual recognition memory showed a median score of 60.5%, and the Rose attention measure from that test showed a median score of 37.9. The association between fetal mercury exposure and neurodevelopmental endpoints was examined by multiple regression analyses. After adjusting for covariates, no association between the maternal hair mercury level during pregnancy and an adverse neurodevelopmental outcome of the child was identified at 6 1/2 months of age.