THURSDAY, Feb. 15 (HealthDay News) -- Children whose mothers ate at least three servings of fish a week during pregnancy had higher scores in tests of mental function in their early years.

That's the conclusion of a new British-American study that conflicts with advice on fish consumption for pregnant women given by U.S. government agencies.

"For the baby's development, at the level of 12 ounces a week during pregnancy, the beneficial effects of the nutrients in fish far outweigh the risk," said Dr. Joseph Hibbeln. He is a clinical investigator at the U.S. National Institute of Alcohol Abuse and Alcoholism and lead author of a report on the study in the Feb. 17 issue of the journal The Lancet.

That assessment contradicts advice given by two U.S. agencies, the Environmental Protection Administration and the Food and Drug Administration, which issued an advisory in 2004 telling pregnant women to avoid eating more than 340 grams of fish -- about 12 ounces a week -- because of the danger of mercury poisoning.

The new study found that maternal seafood intake during pregnancy of less than 340 grams a week was associated with increased risk of children being in the bottom 25 percent of verbal IQ at 8 years of age and with suboptimum performance on tests of social behavior, fine motor activity, communication and social development.

Hibbeln said the FDA and the EPA have been briefed on the results of the study.

Suzanne Ackerman, a spokeswoman for the EPA, said, "We looked at all the relevant information before issuing the guidelines. It is much too early to say whether one study will change the guidelines."

Veronica Castro, an FDA spokeswoman, said, "We have made no changes to our current information regarding pregnant women and seafood consumption."

The new study followed the children of 11,875 women living in Bristol, England, who had expected delivery dates between April 1991 and December 1992. The women were sent postal questionnaires about their diet four times during pregnancy and then periodically afterward about their children's social and developmental outcomes.

"We noted that children of mothers who ate small amounts (less than 340 grams per week) of seafood were more likely to have suboptimum neurodevelopmental outcomes than children of mothers who ate more seafood than the recommended amounts," the researchers reported.

The benefits "most likely" came from the high content of omega-3 fatty acids in fish, Hibbeln said. As for mercury, the fish consumed in England "appears to have more methyl mercury in it than the fish eaten in the United States, particularly tuna," he said.

"Our study has shown that the benefits of eating fish do outweigh the risks," said Jean Golding, professor emeritus of pediatric epidemiology at the University of Bristol and a member of the research team. "That might be at least three portions a week. Not at every meal, but we couldn't see with the information we had any harm from eating fish."

Dr. Gary Myers is a professor of neurology, pediatrics and environmental medicine at the University of Rochester in New York, and co-author of an accompanying editorial in the journal. He said the study "says that it is very important for children's cognitive development to get adequate amounts of long-chain fatty acids."

And there are few other dietary sources of those omega-3 fatty acids, he said, such as walnuts and flaxseeds.

"This article really points out the benefits of eating fish," Myers said. "It is important when people think about children to keep a balanced view of these things. There are no documented cases of people being damaged by eating fish. Reports of damage are based on epidemiological studies that are complex and difficult to interpret at times."

He said that one major problem with conducting a similar study in the United States is that "it is hard to get together people who eat large amounts of fish. Finding a group of individuals to study is not easy."

Asked what he would recommend to pregnant women, Myers answered with a question: "You know for a fact that eating fish improves your child's cognitive development. Someone tells you there might be a risk of eating mercury. Which would you choose?"

More information

For more on nutrition and pregnancy, visit the U.S. National Women's Health Information Center.