Prenatal Mercury Exposure, Fish Intake and Neurocognitive Development During First Three Years of Life: Prospective Cohort Mothers and Children's Environmental Health (MOCEH) Study

Objectives: In this prospective cohort study, the effects of prenatal Hg exposure on neurocognitive development during the first 3years of life were investigated.

Methods: The maternal blood levels of Hg were assessed during pregnancy and in cord blood. Maternal fish intake was assessed by interviewing the weekly frequency of fish intake during pregnancy. Maternal n-3 and n-6 fatty acid intake was estimated based on 24h recall food intake interview. The mental (MDI) and psychomotor (PDI) development index scores were assessed using the Bayley Scales of Infant Development at 6, 12, 24, 36months of age.

Results: The geometric mean of the maternal blood Hg concentration was 3.3μg/L (10th percentile=1.81; 90th=5.91) during the early pregnancy, 3.0μg/L (10th=1.68; 90th=5.57) during late pregnancy, and 5.1μg/L (10th=2.94; 90th=8.93) in cord blood. After adjusting for weekly frequency of fish intake, the blood Hg concentrations during early pregnancy showed association with the adjusted MDI (β=-0.408, p=0.048) and PDI scores (β=-0.550, p=0.031) at 6months. After further adjusting for n-3 and n-6 fatty acids estimated based on 24h recall of food intake, the blood Hg concentrations during early pregnancy showed association with the MDI (β=-0.489, p=0.026) and PDI (β=-0.664, p=0.015) at 6months.

Conclusion: These results show that prenatal Hg exposure during early pregnancy adversely associated with early neurodevelopment during infancy, after adjusting for fish and n-3, n-6 fatty acid intake. Consuming fish high in fatty acids and low in Hg during early pregnancy may be important to neurocognitive development at early infancy.