FRIDAY, March 20, 2020 (HealthDay News) -- Advice on eating fish while pregnant has flip-flopped over the years. Now, a new study suggests that the benefit of eating fish in moderation during pregnancy outweighs the risk.

Fish is a major source of omega-3 fatty acids, which are important for a developing fetus. But some fish -- such as swordfish, shark and mackerel -- can contain high levels of mercury, which can cause neurological damage.

The new study included 805 mother-child pairs in five European countries. During pregnancy, the women were asked about their fish consumption and tested for mercury exposure.

When their children were between 6 and 12 years of age, the kids' metabolic health was assessed. Metabolic health includes factors such as waist circumference, blood pressure and cholesterol levels.

The University of Southern California (USC) researchers found that children whose moms ate fish one to three times per week during pregnancy were more likely to have better metabolic health than kids whose mothers ate fish less than once a week during pregnancy.

But the benefits decreased if their mothers ate fish more than three times a week during pregnancy, according to the study published online March 16 in JAMA Network Open.

"Fish is an important source of nutrients, and its consumption should not be avoided," said senior investigator Dr. Leda Chatzi, an associate professor of preventive medicine at the Keck School of Medicine of USC.

"But pregnant women should stick to one to three servings of fish a week as recommended, and not eat more, because of the potential contamination of fish by mercury and other persistent organic pollutants," she advised in a school news release.

Study co-author Nikos Stratakis, a postdoctoral scholar, pointed out that fish can be a common route of exposure to dangerous chemical pollutants.

"It is possible that when women eat fish more than three times a week, that pollutant exposure may counterbalance the beneficial effects of fish consumption seen at lower intake levels," Stratakis said.

The researchers now plan to examine the effects of consuming different types of fish with different nutrients and mercury levels. They also expect to follow the children in the study until their mid-teens.

More information

The U.S. Food and Drug Administration offers advice about fish consumption during women's childbearing years.