Women who eat seafood while pregnant may be boosting their children's IQ, says new research -- contradicting current recommendations that pregnant women limit seafood to avoid mercury.

The study concluded that women who ate more than 340 grams a week of fish or seafood -- the equivalent of two or three servings a week -- had smarter children with better developmental skills.

Children whose mothers ate no seafood were 48 per cent more likely to have a low verbal IQ score, compared with children whose mothers ate high amounts of seafood, the researchers found.

The study, led by Dr. Joseph Hibbeln of the U.S. National Institutes of Health, tracked the eating habits of 11,875 pregnant women in Bristol, Britain.

At 32 weeks into their pregnancy, the women were asked to fill out a seafood consumption questionnaire. They were sent questionnaires four more times during their pregnancy, and then up to eight years after the birth of their child.

Researchers examined the children's social and communication skills, their hand-eye co-ordination, and their IQ levels. They concluded that fish in a mother's diet did affect their children's development.

But since the study was based on self-reporting methods, the results cannot be considered entirely definitive.

Seafood for pregnant women has remained controversial, because the food contains both nutrients and toxins.

Fish is a rich source of omega-3 fatty acids, essential to brain development, is low in saturated fat and contains high-quality protein. But it can also contain mercury, which can cross the placenta and build up in a fetus' nervous system.

Large saltwater fish are of particular concern. Health Canada recommends that pregnant women, women of child-bearing age, and small children not consumer more than one meal per month of swordfish, shark and fresh tuna.

Other Canadians should restrict consumption to one meal per week.

(Canned tuna is considered safer, because the species used tend to be smaller and shorter lived than those used in the fresh and frozen market, and therefore, the level of mercury found in canned tuna tends to be lower.)

While experts believe further research is necessary to confirm these conclusions, the study's failure to find evidence of increased harm from eating fish is significant.

Because seafood contains both nutrients and toxins, it remains a dilemma for regulatory authorities what kinds of recommendations should exist for pregnant women.

Hibbeln suggests that eating even more than three portions of fish or seafood a week could be beneficial to developing babies.

"we found that when you look at fish as a whole, the entire nutritional benefits of fish far outweigh the typical trace contaminants of neurotoxins found in fish," he told CTV Newsnet from Washington, adding that even fish oil capsules are beneficial.

The study was primarily funded by Britain's Medical Research Council, the Wellcome Trust, the University of Bristol, and the British government.

The study is published in The Lancet.