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Pregnancy and fish: What's safe to eat?

By Mayo Clinic staff
Original Article:  http://www.mayoclinic.com/health/pregnancy-and-fish/PR00158

Pregnancy and fish: What's safe to eat?

If you're confused about whether it's safe to eat seafood during your pregnancy, you're not alone. Understand the guidelines for pregnancy and fish.

By Mayo Clinic staff
Photo of Roger Harms, M.D.
Roger Harms, M.D.

If you're pregnant, you might feel like you need to become a nutrition expert overnight. After all, what you eat and drink — and what you avoid — influences your baby's development. Some choices are logical, such as eating plenty of fruits and vegetables and eliminating alcohol from your diet. But what about seafood? When it comes to pregnancy and fish, researchers give mixed reports.

Here, Roger Harms, M.D., a pregnancy specialist at Mayo Clinic, Rochester, Minn., and medical editor of "Mayo Clinic Guide to a Healthy Pregnancy," offers practical advice about pregnancy and fish.

What's the link between pregnancy and fish?

Seafood can be a great source of protein and iron — crucial nutrients for your baby's growth and development. In addition, the omega-3 fatty acids in many fish can promote your baby's brain development.

But some types of seafood — particularly large, predatory fish such as shark, swordfish, king mackerel and tilefish — may contain high levels of mercury. Although the mercury in seafood isn't a concern for most adults, special precautions apply if you're pregnant or planning to become pregnant. If you regularly eat fish high in mercury, the substance can accumulate in your bloodstream over time. In turn, too much mercury in your bloodstream could damage your baby's developing brain and nervous system.

How much seafood is recommended?

The Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) say pregnant women can safely eat up to 12 ounces (340 grams) of seafood a week. Similarly, the 2010 Dietary Guidelines for Americans recommend 8 to 12 ounces of seafood a week for pregnant women — or about two average meals.

Not all researchers agree with these limits, however, citing a study that noted no negative effects for women who ate more seafood than the FDA-approved guidelines.

What's safe to eat?

Choose seafood that's low in mercury, such as:

  • Shrimp
  • Crab
  • Salmon
  • Pollock
  • Catfish
  • Cod
  • Tilapia

Canned light tuna is another good choice — but limit albacore tuna, chunk white tuna and tuna steak to no more than 6 ounces, or 170 grams, a week.

Are there other guidelines for pregnancy and fish?

Consider these precautions:

  • Avoid large, predatory fish. To reduce your exposure to mercury, don't eat shark, swordfish, king mackerel or tilefish.
  • Avoid raw fish and shellfish. To avoid ingesting harmful bacteria or viruses, avoid raw fish and shellfish — especially oysters and clams — and anything you know was caught in polluted water. Refrigerated smoked seafood, such as lox, also is off-limits.
  • Understand local fish advisories. If you eat fish from local waters, pay attention to local fish advisories. Larger game fish contaminated with chemical pollutants could potentially harm a developing baby. If advice isn't available, limit fish from local waters to 6 ounces (170 grams) a week and don't eat other fish that week.
  • Cook seafood properly. Cook fish to an internal temperature of 145 F (63 C). The fish is done when it separates into flakes and appears opaque throughout. Cook shrimp, lobster and scallops until they're milky white. Cook clams, mussels and oysters until their shells open. Discard any that don't open.

Are fish oil supplements safer than fresh or frozen fish?

While some research has shown that women who take fish oil supplements during pregnancy might improve their children's hand-eye coordination, the findings are preliminary — and other research doesn't support a link between fish oil supplements and improved cognitive or language development in children. The safety of fish oil supplements during pregnancy also has yet to be established. More studies are needed before fish oil supplements can be routinely recommended during pregnancy.

Are there other ways to get omega-3 fatty acids?

Most research on pregnancy and omega-3 fatty acids focuses on seafood or supplements. Other sources of omega-3 fatty acids — such as flaxseed oil, canola oil, soybean oil, ground flaxseed and walnuts — can be part of a healthy diet as well. However, researchers haven't yet determined whether omega-3 fatty acids from plant sources can promote fetal brain development.

What's the bottom line?

Though mercury can harm a developing baby's brain, eating average amounts of seafood containing low levels of mercury during pregnancy hasn't been shown to cause problems. And the omega-3 fatty acids in many types of fish — especially salmon and tuna — can promote healthy cognitive development. As long as you avoid fish known to be high in mercury or contaminated with pollutants, fish can be a regular part of your healthy-eating plan during pregnancy.

References
  1. Makrides M, et al. Effect of DHA supplementation during pregnancy on maternal depression and neurodevelopment of young children. JAMA. 2010;304:1675.
  2. Oken E. Risks and benefits of fish consumption and fish oil supplements during pregnancy. http://www.uptodate.com/home/index.html. Accessed Oct. 28, 2010.
  3. What you need to know about mercury in fish and shellfish. United States Environmental Protection Agency. http://water.epa.gov/scitech/swguidance/fishshellfish/outreach/advice_index.cfm. Accessed Oct. 28, 2010.
  4. Fresh and frozen seafood: Selecting and serving it safely. U.S. Food and Drug Administration. http://www.fda.gov/food/resourcesforyou/consumers/ucm077331.htm. Accessed Oct. 29, 2010.
  5. Oken E, et al. Associations of maternal fish intake during pregnancy and breastfeeding duration with attainment of developmental milestones in early childhood: A study from the Danish national birth cohort. American Journal of Clinical Nutrition. 2008;88:789.
  6. Hibbeln JR, et al. Maternal seafood consumption in pregnancy and neurodevelopmental outcomes in childhood (ALSPAC study): An observational cohort study. The Lancet. 2007;369:578.
  7. Dunstan JA, et al. Cognitive assessment of children at age 2 1/2 years after maternal fish oil supplementation in pregnancy: A randomized controlled trial. Archives of Childhood Diseases: Fetal and Neonatal Edition. 2008;93:F45.
  8. Position of the American Dietetic Association: Nutrition and lifestyle for a healthy pregnancy outcome. Journal of the American Dietetic Association. 2008;108:553.
  9. Dietary Guidelines for Americans 2010. U.S. Department of Health and Human Services. http://www.cnpp.usda.gov/Publications/DietaryGuidelines/2010/PolicyDoc/PolicyDoc.pdf. Accessed Jan. 31, 2011.
  10. Position of the American Dietetic Association: Vegetarian diets. Journal of the American Dietetic Association. 2009;109:1266.
  11. Month 5 (weeks 17 to 20). Your Pregnancy and Childbirth: Month to Month. 5th ed. Washington, D.C.: American College of Obstetricians and Gynecologists; 2010:85.
  12. Kris-Etherton PM, et al. Polyunsaturated fatty acids in the food chain in the United States. The American Journal of Clinical Nutrition. 2000;71:179S.
  13. Fish facts. The National Women's Health Information Center. http://www.4women.gov/pregnancy/mom-to-be-tools/fish-facts.pdf. Accessed Feb. 11, 2011.
PR00158 Feb. 26, 2011

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