Mercury and fish

Fish is an easy-to-prepare food. It is high in protein, low in fat and full of heart-healthy nutrients. But pollution in our oceans, lakes, rivers and streams is leaving some fish with toxic levels of mercury, which is especially damaging to fetuses, babies and children.

What is mercury?
Mercury is a metal found naturally in many forms, all of which are poisonous. It's used in thermometers, batteries and dental fillings and is emitted from power plants and other industrial activity. These emissions fall into bodies of water where they collect in fish, accumulating over time and in bigger fish. Americans get most of their exposure to mercury from eating these mercury-contaminated fish.

If a woman is exposed to high levels of mercury before or while she is pregnant, her health and the baby's health are threatened.

What are the health risks of mercury exposure?
Mercury damages many parts of the body, including the nervous system, the lungs, the kidneys, vision, and hearing. The seriousness of the risk depends upon how much mercury a person is exposed to. The risk is especially great for fetuses and children.

Babies who are exposed to mercury while in the womb can suffer severe damage to the nervous system and may die. They may have brain damage, learning disabilities and hearing loss.

How much fish can a pregnant woman safely eat?
To learn more about how much fish a pregnant woman can safely eat, read the article about healthy eating.

February 2007

Most common questions

How much weight should I gain during my pregnancy?

The exact amount of weight you need to gain depends on how much you weigh before pregnancy and your Body Mass Index (BMI). Below are some guidelines, but talk to your health provider about your specific pregnancy weight gain goals.

If you began pregnancy at a healthy weight, you should gain 25 to 35 pounds over the 9 months. If you gain between 1 and about 4 ½ pounds in the first trimester, you should put on about 1 pound every week in the second and third trimesters.

If you began pregnancy underweight, you should probably gain about 28 to 40 pounds. If you gain between 1 and about 4 ½ pounds in the first trimester, try to gain slightly over a pound a week in the second and third trimesters.
If you began pregnancy overweight, you should gain only 15 to 25 pounds over the 9 months. If you gain between 1 and about 4 ½ pounds in the first trimester, you should put on slightly over ½ pound every week in the second and third trimesters. While you don't want to gain too much weight, never try to lose weight during pregnancy because that could harm your baby.

If you were obese (with a BMI over 30) at the start of your pregnancy, you should gain only 11 to 20 pounds over the 9 months. If you gain between 1 and about 4 ½ pounds in the first trimester, aim for gaining slightly under ½ pound every week in the second and third trimesters.

Is it safe to eat cold cuts when I'm pregnant?

It's not safe for pregnant women to eat deli meats (such as ham, turkey, salami and bologna) or hot dogs unless the food has been thoroughly heated and is steaming hot. These foods can cause a form of food poisoning called listeriosis and is caused by bacteria. Heating deli meats until steaming hot will kill the bacteria if it's present.

Listeriosis is especially dangerous during pregnancy. Most people don't get sick when they eat food contaminated with listeria. But healthy pregnant women are more likely than other healthy adults to get listeriosis and are more likely to become dangerously ill from it.

The flu-like symptoms of listeriosis can sometimes advance to potentially life-threatening meningitis (infection of the membranes covering the brain, with symptoms such as severe headache and stiff neck) and blood infection. Contact your health care provider if you're pregnant and you develop any of these symptoms.

Is it safe to eat fish raw or seared during pregnancy?

You should avoid all raw or seared fish when you're pregnant. (Seared fish are typically not fully cooked throughout.) Raw fish, including sushi and sashimi, and undercooked finfish and shellfish (including oysters, clams, mussels and scallops) are more likely to contain parasites or bacteria than cooked fish. 


Avoid swordfish, shark, king mackerel and tile fish, even when cooked. These fish have more mercury than other fish. Mercury can be transferred to your growing baby and cause serious health problems. Stay away from game fish, too, until you check its safety with your local health department. A game fish is any fish caught for sport, such as trout and bass.


The USDA recommends that pregnant women limit their fish consumption to 12 ounces of a variety of cooked fish per week.


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