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Advice for Patients
Dec 2012

Exposure to Mercury and Consumption of Fish During Pregnancy: A Confusing Picture

Arch Pediatr Adolesc Med. 2012;166(12):1188. doi:10.1001/jamapediatrics.2013.928

The foods that a mother eats during pregnancy affect the health of the baby. Because of the importance of a mother's diet during pregnancy, recommendations have been developed based on research and nutritional guidelines. Some of these diet guidelines for pregnancy include:

  • Eating iron-rich or iron-fortified foods such as meats or meat alternatives, breads, and cereals.

  • Taking a daily folic acid supplement.

  • Eating a well-balanced diet including fruits and vegetables.

  • Eating or drinking calcium-rich foods or milk.

  • Avoiding alcoholic beverages.

One dietary recommendation during pregnancy is to avoid foods with mercury. Mercury is a liquid metal that is a naturally occurring element released by volcanoes and rocks. Much of the mercury that is in bodies of water—and the fish that live in them—comes from air pollution. Exposure to mercury mostly happens in certain types of work, often called “occupational exposure.” Eating fish is the main way that people are exposed to mercury outside of the workplace. Mercury has many negative effects on the body, especially on the brain. The US Environmental Protection Agency and Food and Drug Administration recommend that pregnant women should limit their fish intake to no more than two 6-oz servings a week.

However, fish is a food rich in nutrients. These nutrients include ω-3 fatty acids, which have been shown to benefit brain development. A recent study in the Archives found that exposure to low levels of mercury during pregnancy was associated with attention-deficit/hyperactivity disorder but that moms who eat fish during pregnancy are protected from attention-deficit/hyperactivity disorder. This study shows the difficulty of balancing the benefits of fish with the risks of mercury.

  • Pregnant moms can consider eating fish that are generally lower in mercury. These include shrimp, canned light tuna, salmon, pollack, and catfish.

  • The fish that have the highest levels of mercury are shark, swordfish, king mackerel, and tilefish; these are fish to avoid.

  • Check local advisories about the safety of fish caught in your local lakes, rivers, and coastal areas.

  • If you eat a lot of fish in 1 week and are unsure of its mercury content, 1 week's consumption is not likely to change the level of mercury in your body. Try to cut back on fish for the next week or 2.

For more information

Food and Drug Administration

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Source: Food and Drug Administration

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