A pilot neurodevelopmental study of Seychellois children following in utero exposure to methylmercury from a maternal fish diet

It is not known if fetal neurodevelopmental damage occurs in humans at the low-level methylmercury exposure achieved by eating fish. To address this question, a cohort of 804 children in the Republic of Seychelles was identified who had fetal methylmercury exposure from a maternal diet high in oceanic fish. Mercury was determined by measuring the maternal total hair mercury during pregnancy, a standard index of methylmercury exposure. The median fetal mercury exposure was 6.6 ppm. Children were evaluated once between 5 to 109 weeks of age. Testing included the revised Denver Developmental Screening Test (DDST-R) and a neurological examination. The association between maternal hair mercury levels and developmental outcome was evaluated by multiple logistic regression analysis. Covariates for the child included gender, birth weight, one and five-minute Apgar score, age at testing, and medical problems, and, for the mother, age, tobacco and alcohol consumption during pregnancy, and medical problems. An association between fetal mercury exposure and development was found when DDST-R scores of questionable and abnormal were combined, a procedure used by previous investigators. These results should be viewed with caution since the association disappeared when DDST-R scores of questionable were treated in the standard manner as passes.