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Eating Fish While Pregnant Pays Off, USC Study Says

Fish is a major source of omega-3 long-chain polyunsaturated fatty acids, which are important for the developing fetus. But, some types, such as swordfish, shark and mackerel, can contain high levels of mercury -- a potent toxin that can cause permanent neurological damage.

Judith, 28, had planned a "freebirth" with no doctors or midwives - just her, her husband and a friend. As she reached the 45th week of her pregnancy, she turned to online pregnancy groups for help, whose members urged her not to seek a doctor.
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What to Know

  • The study looked at 805 moms-to-be
  • The children of women who ate fish from one to three times a week had lower metabolic syndrome scores than the children of women who ate fish less than once a week
  • But the benefit declined if women ate fish more than three times a week

A USC-led study released Monday found that children whose mothers ate fish one to three times a week during pregnancy were more likely to have a better metabolic profile -- despite the risk of exposure to mercury -- than youngsters whose mothers rarely ate fish.

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

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Fish is a major source of omega-3 long-chain polyunsaturated fatty acids, which are important for the developing fetus. But, some types, such as swordfish, shark and mackerel, can contain high levels of mercury -- a potent toxin that can cause permanent neurological damage. Mercury contamination is also found in soil, air, water and plants.

For the study, published today in JAMA Network Open, the researchers looked at 805 mother and child pairs from five European countries participating in a collaborative research project known as the HELIX study, which is following women and their children from pregnancy onward.

During their pregnancy, the women were asked about their weekly fish consumption and tested for mercury exposure. When the children were from 6 to 12 years old, they underwent a clinical examination with various measurements, including waist circumference, blood pressure, high-density lipoprotein cholesterol, triglyceride levels and insulin levels, that were combined to calculate a metabolic syndrome score.

The children of women who ate fish from one to three times a week had lower metabolic syndrome scores than the children of women who ate fish less than once a week. But the benefit declined if women ate fish more than three times a week, according to Nikos Stratakis,  a USC postdoctoral scholar who was one of the study authors.

"Fish can be a common route of exposure to certain chemical pollutants which can exert adverse effects,'' Stratakis said. "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.''

The researchers found that higher mercury concentration in a woman's blood was associated with a higher metabolic syndrome score in her child.

The study also examined how fish consumption by the mother affected the levels of cytokines and adipokines in her child. Those biomarkers are related to inflammation, a contributor to metabolic syndrome.

Compared with low fish intake, moderate and high fish consumption during pregnancy were associated with reduced levels of proinflammatory cytokines and adipokines in the children.

According to USC, it's the first human study to show that the reduction in those inflammation biomarkers could be the underlying mechanism explaining why maternal fish consumption is associated with improved child metabolic health.

The researchers now plan to look at the effects of consuming different types of fish with different nutrients and mercury levels and to follow up on the children in the study until they are ages 14-15.

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In addition to five USC Keck School researchers listed as study authors, the study team included researchers from the CRG/UPF Proteomics Unit, Barcelona, Spain; University of Crete, Greece; Norwegian Institute of Public Health, Oslo; Universite de Paris, France, among others.

The study was supported by the European Community Seventh Framework Program and by the National Institute for Health Sciences.

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