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?
Here, Roger W. 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, iron and zinc — 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 — can 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?
Eat a variety of seafood that's low in mercury and high in omega-3 fatty acids, such as:
- Atlantic and Pacific mackerel
Other safe choices include shrimp, pollock, catfish and canned light tuna. However, limit albacore tuna and tuna steak to no more than 6 ounces (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 uncooked fish and shellfish. To avoid ingesting harmful bacteria or viruses, avoid uncooked fish and shellfish, including sushi, sashimi and refrigerated uncooked seafood labeled nova style, lox, kippered, smoked or jerky.
- Understand local fish advisories. If you eat fish from local waters, pay attention to local advisories. 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 there other ways to get omega-3 fatty acids?
Beyond seafood, other sources of omega-3 fatty acids include:
- Foods. Flaxseed — ground seeds or oil — canola oil, walnuts, sunflower seeds, pine nuts and soybeans (edamame) are all good sources of omega-3 fatty acids.
- Fortified foods. Yogurt, milk and eggs can be fortified with omega-3 fatty acids.
- Supplements. Supplements typically contain fish oil or omega-3 fatty acids from marine plant sources. Talk to your doctor before taking any supplement.
Keep in mind, however, that researchers haven't yet determined whether omega-3 fatty acids from plant sources can promote fetal brain development. While pregnant women can get omega-3 fatty acids from many sources, most experts recommend eating seafood for this purpose.
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.