(HealthDay News) – The risk of developing attention-deficit/hyperactivity disorder (ADHD) is higher with low-level prenatal mercury exposure, but lower with maternal fish consumption during pregnancy, according to a study published online Oct 8 in the Archives of Pediatrics & Adolescent Medicine.

Sharon K Sagiv, PhD, MPH, from the Boston University School of Public Health, and colleagues examined the association between peripartum maternal hair mercury levels (421 subjects) and maternal report of fish consumption during pregnancy (515 subjects) on ADHD-related behavior in their children at 8 years of age.

After taking possible confounding factors into account, the researchers found that mercury exposure was associated with inattention and impulsivity/hyperactivity, with an apparent threshold at ≥1µg/g of mercury. At this level of mercury, the risk ratio for mild/markedly atypical inattentive behaviors was 1.4, while the risk ratio for impulsive/hyperactive behaviors was 1.7. In contrast, children of women who reported consuming more than two servings of fish a week during pregnancy had a reduced risk of ADHD-related behaviors, particularly impulsive/hyperactive behaviors, with a relative risk of 0.4.

“These findings underscore the difficulties of balancing the benefits of fish intake with the detriments of low-level mercury exposure in developing dietary recommendations in pregnancy,” Sagiv and colleagues conclude.

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