Eating seafood during pregnancy provides many health benefits, including healthy fats that aid your baby’s brain and eye development. However, some types of seafood contain high levels of mercury, a toxic metal that can be harmful to a developing baby’s nervous system if consumed in large amounts.
What is mercury and why is it harmful during pregnancy?
Mercury is a natural occurring metal that is found in air, water, and soil. It makes its way into waterbodies and accumulates in the tissues of fish and shellfish. When pregnant women eat seafood containing high levels of mercury, it can be absorbed into their bloodstream and pass through the placenta, potentially affecting the developing fetus.
The effects of mercury exposure on a developing baby may include:
- Impaired cognitive thinking
- Memory and motor skills issues
- Delayed language and speech development
- Vision and hearing problems
To limit mercury exposure, it’s important for pregnant women to avoid eating seafood that typically has high mercury levels. The Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) provide guidelines on recommended seafood consumption during pregnancy.
Which seafood has high mercury levels?
The seafood that tends to have the highest mercury concentrations includes:
- King mackerel
- Orange roughy
- Bigeye tuna
Many of these fish are large, long-lived predatory species that accumulate high amounts of mercury through their diet over time. The FDA recommends avoiding these fish completely during pregnancy because they almost always have mercury levels that exceed safety thresholds.
All species of shark tend to have very high mercury concentrations. Studies have found mercury levels in shark meat ranging from 0.98–4.54 ppm (parts per million), with some species like bull sharks exceeding 4.0 ppm.
Swordfish is another fish known for its characteristically high mercury content. The average mercury level in swordfish is around 1.6 ppm, often surpassing the FDA limit of 1.0 ppm.
King mackerel is a large mackerel species that can weigh over 40 lbs. It’s high up on the food chain, contributing to high mercury accumulation. King mackerel sold on the U.S. market has averaged around 1.4 ppm mercury.
Research has found mercury concentrations between 1.3–1.9 ppm in blue marlin and 0.7–1.2 ppm in striped marlin filets. Both considerably exceed the safe levels for pregnant women.
Orange roughy is a deep sea fish with an especially long lifespan, living up to 150 years. This allows its mercury levels to become significantly elevated over time. Orange roughy has been found to contain mercury concentrations of 0.54–1.6 ppm.
Tilefish inhabit the Gulf of Mexico where mercury pollution is a major problem. Mercury levels in golden tilefish caught in these waters average 1.450 ppm, topping the charts for the highest mercury concentration in any fishery.
Bigeye tuna is a large, predatory tuna species that can weigh over 400 lbs. It’s high up on the food chain and slow to mature, leading to high mercury accumulation over many years. Bigeye tuna sushi has been tested to contain mercury levels exceeding 1.0 ppm.
Should I avoid canned tuna?
Canned light tuna is considered safe to eat during pregnancy. It offers various nutrients like omega-3s, vitamin D, selenium, and lean protein. According to the FDA and EPA’s calculations, you can safely eat up to 6 ounces (2 to 3 regular cans) of canned light tuna per week when pregnant or breastfeeding.
However, it’s best to avoid canned albacore (white) tuna because it contains around 3 times more mercury than the smaller tuna species used in light tuna. The recommend intake is no more than 6 ounces of albacore tuna per week.
What are the best low mercury fish to eat?
To get the benefits of eating seafood during pregnancy without the mercury risks, choose fish and shellfish that are lower in mercury, such as:
- Atlantic mackerel (not king)
These types of seafood are low on the food chain and have short lifespans, which limits how much mercury they accumulate. The FDA encourages eating 8 to 12 ounces per week of low mercury seafood during pregnancy for optimal health benefits.
Salmon is one of the most popular low mercury fish. Farmed salmon tends to have less mercury than wild caught since they are directly fed a controlled diet. Salmon is rich in omega-3 fatty acids that promote your baby’s brain and eye development.
Shrimp have very low mercury levels, with farmed shrimp containing the least. Shrimp provide protein, vitamin D, selenium, and antioxidant carotenoids for pregnancy health.
Alaskan pollock is a whitefish that is low in mercury and can be a good alternative to riskier fish like tuna and swordfish. It contains omega-3 fatty acids, vitamin B12, and selenium.
Popular catfish like channel catfish, blue catfish, and pangasius have minimal mercury and offer an excellent source of lean protein during pregnancy. Farm-raised catfish tends to contain lower mercury than wild.
Cod like Pacific cod and Atlantic cod have white, flaky meat that is low in mercury. Cod is rich in healthy fats, protein, and vitamin B12 which provides various benefits during pregnancy.
Tilapia is a popular pregnancy-safe fish choice. It contains high quality protein to support babies development along with omega-3s, vitamin B12, potassium, and magnesium.
Should I avoid all raw seafood?
Raw seafood poses a high risk for foodborne illnesses during pregnancy. Bacteria and parasites found in some raw seafood can cause food poisoning that may severely affect the health of your unborn baby.
It’s essential to cook seafood thoroughly to an internal temperature of 145°F (63°C) to kill any potential pathogens present. Avoid eating any raw or undercooked fish and shellfish, such as:
- Lightly cooked or seared fish
- Raw oysters and clams
- Roe (fish eggs)
Smoked seafood is also considered unsafe unless it has been cooked to a proper temperature. Refrigerated smoked seafood found in the deli section of groceries may still contain active pathogens.
Raw oysters and clams
Raw oysters, mussels, and clams should always be avoided during pregnancy. They present the highest risk for viruses, bacteria, and parasites that severely attack the health of pregnant women and their babies.
Sushi containing raw or undercooked fish, especially high mercury fish like tuna, should be avoided completely when pregnant. However, sushi containing fully cooked ingredients like cooked fish, shrimp, eel, avocado, cucumber or imitation crab is generally safe.
Ceviche is a seafood dish where raw fish or seafood is “cooked” by soaking in lemon or lime juice. However, the acidic marinade does not destroy harmful pathogens, so ceviche should always be avoided during pregnancy.
Tips for eating seafood safely
Here are some tips for safely eating seafood during pregnancy:
- Consume fish that are lower in mercury and limit albacore tuna to 6 oz per week.
- Eat a variety of fish to minimize exposure to any one source of pollutants.
- Check local fish advisories about safety of fish caught from local lakes, rivers, and coastal areas.
- Cook all seafood thoroughly to at least 145°F.
- Avoid raw or undercooked fish or shellfish.
- Order fully cooked fish when eating out and avoid risky items like sushi and ceviche.
- Refrigerate seafood properly and eat leftover seafood within 2 to 3 days.
During pregnancy, seafood can provide many enriching nutrients essential for you and your baby’s health. However, it’s important to avoid fish with characteristically high mercury levels that may harm your baby’s development. Stick to low mercury seafood options like salmon, shrimp, pollock, catfish, and cod that offer optimal nourishment without the mercury risks. Always cook seafood fully, avoid raw or undercooked items, and be mindful of food safety practices when handling, storing, and consuming seafood.