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An alliance between The Lempert Report and The Center for Food Integrity

Pregnant Women and Fish Intake Impact on Children

Pregnant Women and Fish Intake Impact on Children

Health and Wellness

August 24, 2008

For years, pregnant women have heard the familiar warning from their doctors on limiting fish consumption during pregnancy due to mercury risks. Now, a new study from Harvard Medical School and the University of Michigan takes both fish dangers andbenefits into consideration.
The study, which looked at 341 mother-child pairs in Massachusetts, found that higher fish intake was associated with better child cognitive test performance at age three, while higher mercury levels were associated with poorer test scores.
Mothers were studied during their second trimester where they completed a food questionnaire on the types and amount of fish and seafood consumed. They also submitted blood specimens to check for mercury levels. Later, the resulting children were tested at the age of three on vocabulary, visual development and motor skills.
The 12% of women who ate the most fish (more than two weekly servings) during their second trimester delivered children with the highest scores on two cognitive tests. There was no advantage of fish consumption at or below two weekly servings compared with never.
Children of women with mercury levels below the top tier and fish intake above two weekly servings scored the highest on visual and motor tests. Children of mothers who consumed up to two weekly servings of fish but had mercury levels in the top tier had somewhat lower visual and motor tests.
In general, women who consumed more fish had higher mercury levels. This higher prenatal mercury exposure was associated with lower test scores at age three. Strangely though, there was no overall adverse effect on child development withhigher maternal fish intake. In fact, consuming fish more than twice a week prenatally led to higher child performance on language and visual motor skills tests.
The type of fish consumed – in addition to the amount – seems to play a role as well. Eight percent of the mothers who reported eating canned tuna at least twice weekly had children with higher cognitive scores. However, the three percent who reported consuming more than two weekly servings of fish other than canned tuna scored higher on the visual and motor test, but not on the verbal test.
These findings are especially interesting in light of the current EPA recommendations. The EPA suggests that pregnant women both avoid consuming fish high in mercuryand limit their total fish intake to no more than two six-ounce servings per week. When this recommendation was released in 2001, many pregnant women decreased their fish intake – a finding previously reported by the same group of investigators.
“One of the problems with the FDA/EPA advisory is that although it was intended to limit mercury intake, it doesn’t provide a great deal of direction about which fish types are safer to eat, and which fish types are less safe,” says Dr. Emily Oken, one of the study authors from Harvard Medical School. “Women can eat more fish than the FDA recommends but still not get too much mercury, by choosing fish types lower in mercury.”
Fish and other seafood are the primary dietary source for docosahexaenoic acid or DHA, a fatty acid that is important for early brain development. Since most pregnant women do not consume enough DHA, limiting fish consumption (without DHA supplementation) may reduce access to this nutrient.
Recommendations for fish consumption during pregnancy should take into consideration both the benefits of fish and the potential harms from mercury exposure. Retailers, says Oken, could certainly indicate which fish types are likely to be lower in mercury and other contaminants, as well as which types are likely to behigher in Omega-3 fatty acids. And the EPA and FDA have roles to play too.
“The EPA and FDA need to refine their message, to give women more guidance that there are many types of fish that are very safe to consume more frequently than two weekly servings,” says Oken. “In the meantime, women can look for themselves to see which fish types are lower in mercury on places such as the FDA website.”
For a list of mercury levels in fish, visit: