Pregnant women have always been advised to limit intake of fish as those contaminated with mercury can adversely affect the baby's brain.
The study also discovered that children born to women who ate more than two servings of fish a week during pregnancy were about half as likely as children born to women who ate less fish to have serious problem with attention and hyperactivity at school.
"We saw dramatic protection against these behaviors," says researcher Sharon K. Sagiv, PhD, MPH, an assistant professor of environmental health at Boston University.
"This is only one study. More studies should look at this. But if indeed eating more fish does seem to be protective across different studies, that's an important public health message," Sagiv says.
The study also found that children exposed to high levels of mercury in the womb were more likely to portray signs of attention deficit hyperactivity disorder (ADHD) in school.
"Eating fish is good for brain development," Sagiv says. "But eating fish high in mercury is a risk for brain development."