The Seychelles Child Development Study: Background, Design, and Results Through 66 Months of Age
Philip W. Davidson
University of Rochester School of Medicine and Dentistry

The Seychelles Child Development Study (SCDS) is testing the hypothesis that there is an association between prenatal exposure to methylmercury (MeHg) from maternal fish consumption and child development. We are longitudinally following a large inception cohort (n=779) of mother-child pairs in the Republic of Seychelles where 85% of the population consumes marine fish daily. The mean prenatal exposure in maternal hair is about 7 ppm while other toxic exposures (e.g., lead, alcohol, PCBs and pesticides) are too low to be confounders. This presentation describes the study design, test batteries, analysis plan, and reviews the results of developmental and neurodevelopmental examinations through 66 months of age. Test results show the expected associations between co-variates and developmental endpoints. No adverse association between prenatal exposure and any developmental endpoint has been found.

The Seychelles Child Development Study: Testing and Results at 9 years of Age
Gary J. Myers
University of Rochester School of Medicine and Dentistry

The Seychelles Child Development Study (SCDS) is testing the hypothesis that there is an association between prenatal exposure to methylmercury (MeHg) from maternal fish consumption and child development. This longitudinal study enrolled 789 mother-child pairs at six months of age and this talk describes the results of the children's fifth neurodevelopmental evaluation at 9 years of age. The evaluation consisted of two three-hour test batteries given individually. All of the tests have been commonly used in previous developmental neurotoxicological studies. The tests examined global and domain specific abilities and included nearly all of the tests previously reported to show an adverse association with prenatal MeHg exposure. They specifically tested cognition (memory, attention, executive functions) and learning, perceptual, motor, social and behavioral abilities.

A total of 21 primary endpoints were analyzed for their relationship with prenatal MeHg exposure. Test results showed the expected associations between co-variates and developmental endpoints, as have tests from previous evaluations of this cohort. Two out of 21 endpoints showed a significant association with prenatal exposure; one association was adverse (the grooved pegboard, non-dominant hand) and the other was beneficial (Conner's Teacher Rating Scale, ADHD Index). No other significant associations between exposure and outcome were found. These findings do not support an association between prenatal exposure to MeHg from uncontaminated ocean fish consumption and adverse neurodevelopmental consequences in a population not exposed to other neurotoxins.

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