Seven types of fish should be completely avoided during pregnancy due to dangerously high mercury levels: king mackerel, marlin, orange roughy, shark, swordfish, Gulf of Mexico tilefish, and bigeye tuna. Beyond mercury, raw and certain smoked fish also pose serious infection risks. But fish itself is genuinely important during pregnancy, so knowing what to skip and what to enjoy makes a real difference.
The Seven Highest-Mercury Fish
The FDA and EPA jointly maintain a list of fish with the highest mercury concentrations, labeled “Choices to Avoid” for pregnant women, those who may become pregnant, breastfeeding mothers, and young children. These seven species sit at the top:
- King mackerel
- Marlin
- Orange roughy
- Shark
- Swordfish
- Tilefish from the Gulf of Mexico
- Bigeye tuna
These are all large, long-lived predatory fish. Mercury accumulates as it moves up the food chain, so the bigger and older the fish, the more mercury it stores in its flesh. There’s no amount of cooking or preparation that reduces mercury levels, which is why these species are a flat “avoid” rather than a “limit.”
Why Mercury Matters for Your Baby
The form of mercury found in fish, called methylmercury, is a potent neurotoxicant. It crosses the placenta and reaches the developing brain, where it can interfere with the formation of brain and eye tissue. The third trimester is an especially critical window because that’s when your baby’s brain rapidly accumulates the fatty acids it needs for development, and methylmercury disrupts that process.
The concern isn’t about eating one piece of swordfish by accident. It’s about repeated exposure building up over weeks and months, since mercury leaves your body slowly. That’s why the guidelines focus on patterns of eating rather than single servings.
The Tuna Question
Tuna is one of the most commonly eaten fish, and the answer depends entirely on which type you’re buying. Not all tuna is equal when it comes to mercury.
Canned light tuna is mostly skipjack, a smaller species with mercury levels generally below 0.22 parts per million. At that concentration, one to two servings per week is considered reasonable. Canned white (albacore) tuna is a different story. Albacore runs between 0.22 and 0.95 parts per million, roughly two to four times higher than skipjack. Limiting albacore to about one serving per month is a safer approach during pregnancy. Bigeye tuna, the kind often used in sushi restaurants for high-end tuna dishes, is on the “avoid entirely” list.
If you’re grabbing a can at the store, check the label. “Light” is your lower-mercury option. “White” or “albacore” means you should count it more carefully against your weekly total.
Raw Fish, Sushi, and Ceviche
Mercury isn’t the only risk with fish during pregnancy. Raw or undercooked seafood carries a real chance of bacterial and parasitic infection. Pregnant women are 10 times more likely than the general population to develop a Listeria infection, which can cause miscarriage, stillbirth, or serious illness in newborns.
The CDC lists the following as riskier choices during pregnancy:
- Raw or undercooked fish and shellfish, including sashimi, sushi, and ceviche
- Refrigerated smoked seafood labeled as “nova-style,” “lox,” “kippered,” “smoked,” or “jerky” (unless it’s cooked into a dish like a casserole)
Vacuum-packed smoked fish is a particular concern. Listeria can survive and multiply at refrigerator temperatures, even inside sealed packaging without oxygen. The long shelf life of these products, sometimes up to three weeks, gives the bacteria plenty of time to reach dangerous levels. Smoked salmon on a bagel is a common way people are exposed without realizing the risk.
How to Cook Seafood Safely
Cooking eliminates the Listeria and parasite risk. Fish is safe when cooked to an internal temperature of 145°F (63°C), or more practically, when the flesh turns opaque and flakes easily with a fork. For shellfish like mussels and clams, cook until the shells open. Discard any that stay closed.
Smoked fish is safe if it comes in a shelf-stable, sealed package that doesn’t require refrigeration before opening, or if you cook it into a hot dish. Canned fish and seafood are also safe options because the canning process involves high heat.
Locally Caught Fish
If friends or family catch fish from local lakes, rivers, or coastal waters, check for local fish advisories before eating it. State and tribal governments issue these advisories based on mercury and other contaminant testing in specific bodies of water. You can usually find them through your state’s environmental or health department website.
If no advisory exists for the area where the fish was caught, the EPA recommends eating only one serving and no other fish that week. Local waterways can have contamination levels that vary dramatically from one lake to the next, so store-bought fish is generally more predictable.
Fish You Should Actually Eat
Avoiding high-mercury fish doesn’t mean avoiding fish altogether. In fact, skipping fish entirely during pregnancy means missing out on nutrients that directly support your baby’s brain and eye development. The omega-3 fatty acid DHA is essential for building retinal and brain tissue, and fish is one of the richest dietary sources.
Pregnant women should aim for at least 200 mg of DHA per day. During the third trimester, when fetal brain growth accelerates, some research suggests an optimal intake closer to 535 mg of combined DHA and EPA daily. The FDA recommends two to three servings (8 to 12 ounces) per week of lower-mercury fish. Good options include:
- Salmon (one of the highest in omega-3s)
- Sardines
- Anchovies
- Herring
- Shrimp
- Pollock
- Tilapia
- Cod
- Catfish
- Canned light tuna
These are all small or short-lived species that don’t accumulate significant mercury. Eating a variety rather than the same fish repeatedly also helps spread out any trace contaminant exposure. Two to three servings per week of these fish is not just safe, it’s actively beneficial for your pregnancy.