Maternal prenatal fish consumption and cognition in mid childhood: Mercury, fatty acids, and selenium.
Level 3 - non-randomized controlled study
Prospective longitudinal cohort study (Project Viva)
PubMed 27381635 · doi:10.1016/j.ntt.2016.07.001
What was done
Researchers evaluated 1,068 mother-child pairs (872 with blood samples) from the prospective Project Viva cohort enrolled between 1999 and 2002. Maternal fish intake was assessed at median 27.9 weeks gestation via food frequency questionnaires, and blood was assayed for erythrocyte mercury, erythrocyte selenium, and plasma DHA and EPA. At a median child age of 7.7 years, offspring completed cognitive assessments including the Kaufman Brief Intelligence Test (KBIT), alongside tests of memory and visual-motor abilities. Multivariable linear regression models evaluated associations between exposures and cognitive outcomes, adjusting for maternal intelligence, home environment, and other covariates.
What was found
Mean (SD) maternal prenatal exposures were: fish intake 1.7 (1.5) servings/week, erythrocyte mercury 4.0 (3.6) ng/g, plasma DHA+EPA 98.4 (41.8) mcg/ml, and erythrocyte selenium 205.6 (34.6) ng/ml. Child KBIT verbal scores (mean 112.2, SD 15.0) were not associated with maternal fish intake (0.15 points per unit; 95% CI: -0.50, 0.79), mercury (0.08; 95% CI: -0.18, 0.35), DHA+EPA (0.01; 95% CI: -0.22, 0.24), or selenium (0.20; 95% CI: -0.09, 0.50). Associations with KBIT nonverbal scores, memory, and visual-motor performance were similarly null, and mutual adjustment across biomarkers did not alter these findings.
Why it matters
In populations with moderate maternal fish intake (~1.5 to 2 servings weekly) and relatively low mercury exposure, neither beneficial nutrients (DHA, EPA, selenium) nor toxicant exposures (mercury) during mid-to-late pregnancy showed measurable lasting impacts on mid-childhood general intelligence or visual-motor skills.
Limits
The cohort had moderate, relatively narrow ranges of fish intake and mercury exposure, preventing conclusions about very high or very low intake levels. Dietary intake was self-reported, exposure biomarkers were measured at only a single timepoint during gestation, and residual confounding cannot be ruled out.
Cited by
- contradicts Studies demonstrate that maternal fish intake during pregnancy is correlated with higher intelligence in children at one and seven years of age, with higher maternal mercury serving as a biomarker of higher fish intake.