Pregnancy nutrition can be confusing, especially when it comes to seafood guidelines. Here's help understanding the facts.

Seafood, which includes fish and shellfish, can be a great source of protein, iron and zinc. These are important nutrients for your baby's growth and development. The omega-3 fatty acids in many fish, including docosahexaenoic acid (DHA), also can help with your baby's brain development.

But some types of seafood can have high levels of mercury. These include large, predatory fish such as shark, swordfish, king mackerel and tilefish. And canned chunk white tuna — also called albacore tuna — may be higher in mercury than canned light tuna. 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, mercury can build up in your bloodstream over time. Too much mercury in your bloodstream could damage your baby's developing brain and nervous system.

The Food and Drug Administration (FDA), the Environmental Protection Agency (EPA) and the Dietary Guidelines for Americans recommend that, in a week, pregnant people eat at least 8 ounces (224 grams) and up to 12 ounces (340 grams) of a variety of seafood lower in mercury. That's about 2 to 3 servings a week.

Eat a variety of seafood that's low in mercury and high in omega-3 fatty acids, such as:

• Salmon
• Anchovies
• Herring
• Sardines
• Freshwater trout
• Pacific mackerel

Other safe choices include:

• Shrimp
• Pollock
• Tilapia
• Cod
• Catfish
• Canned light tuna

However, limit white tuna — also called albacore tuna — and tuna steaks to 6 ounces (170 grams) a week.

Take these steps:

• Avoid large, predatory fish. To lower your exposure to mercury, don't eat shark, swordfish, king mackerel or tilefish.
• Skip uncooked fish and shellfish. To avoid harmful bacteria or viruses, don't eat fish and shellfish that has not been cooked. That includes oysters, sushi, sashimi, and refrigerated seafood that hasn't been cooked that is 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.
• Cook seafood properly. Most seafood should be cooked to an internal temperature of 145 degrees Fahrenheit (63 degrees Celsius). Fish is done when it separates into flakes and appears milky white throughout. Cook shrimp and lobster until the flesh is pearly and milky white. Cook clams, mussels and oysters until their shells open. Throw away any that don't open.

Beyond seafood, other sources of omega-3 fatty acids include:

• Foods. Flaxseed — ground seeds or oil — canola oil, walnuts, sunflower seeds and soybeans, also called 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. Many prenatal vitamins also contain DHA. Talk to your health care professional before taking any supplement.

Keep in mind that researchers haven't yet determined whether supplements can promote your baby's brain development. While pregnant people can get omega-3 fatty acids from many sources, most experts advise eating seafood for this purpose.

Mercury can harm a developing baby's brain. But 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 can promote a baby's healthy brain development. As long as you avoid fish known to be high in mercury or contaminated with pollutants, seafood can be a regular part of your healthy-eating plan during pregnancy.