A new study shows slight mercury exposure during pregnancy could be linked to a higher risk of ADHD-related behaviors.

This study, led by Susan Korrick, MD, MPH, of Brigham and Women's Hospital (BWH), and Sharon Sagiv, PhD, MPH, of Boston University School of Public Health, is published in the online version of the Archives of Pediatrics & Adolescent Medicine, and shows that fish consumption for pregnant women can also decrease the risk of ADHD-related behaviors in children.

This twofold possibility can occur because several types of fish have low levels of mercury, allowing pregnant women to consume fish without being exposed to a large amount of mercury. Previous studies have even indicated that the benefits of prenatal fish consumption outweigh the risks.

ADHD (attention-deficit/hyperactivity disorder) affects around ten percent of children worldwide. An individual showing ADHD symptoms has a difficult time focusing on one thing without being distracted by another. They are often restless, fidgety, overactive, and find it problematic to wait in situations, such as having conversations, standing in line, or for their turn to play.

The current study examined 400 children born in New Bedford, Massachusetts between 1993 and 1998. After the mothers gave birth, their hair samples were collected and analyzed for mercury by the researchers. A survey was also given to measure their fish consumption during pregnancy. Researchers performed a follow-up eight years later with the children, conducting standardized tests to check if they exhibited behaviors related to ADHD.

Findings showed an elevated risk of childhood ADHD-related behaviors with raised maternal hair mercury levels. These levels appeared to be less hazardous than previous levels seen in other studies. Experts also found a decreased risk of ADHD-related behaviors, in children whose mothers documented consuming more than two servings of fish per week, more servings than currently recommended by the United States Food and Drug Administration and Environmental Protection Agency.

Dr Korrick commented:

"These findings underscore the difficulties pregnant women face when trying to balance the nutritional benefits of fish intake with the potential detriments of low-level mercury exposure."

Dr. Sagiv agrees, saying:

"Women need to know that nutrients in fish are good for the brain of a developing fetus, but women need to be aware that high mercury levels in some fish pose a risk."

Not examined in this study were the types of fish that are best for a pregnant woman to eat, however, earlier studies have shown women should stay away from fish high in mercury, such as fresh tuna, swordfish, shark, and king mackerel. Good sources of nutrition can be found in fish with low levels of mercury such as haddock, flounder, and salmon. Appropriate fish consumption can be beneficial both to the mother and baby.

Written by Kelly Fitzgerald