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U.S. Department of Health and Human Services

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Food Safety for Moms-To-Be: Before You're Pregnant - Methylmercury

Food Safety for Moms-to-Be

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Methylmercury Matters Before Pregnancy
Seafood can be an important part of a balanced diet. It's a good source of high-quality protein and other nutrients and it's low in fat. However, some fish contain high levels of methylmercury, which can harm an unborn child's developing nervous system - even before conception

So if you're thinking about becoming pregnant, you should be aware of these risks and take steps to prevent exposure to methylmercury. Here are some answers to frequently asked questions about methylmercury.

Methylmercury can build up in a woman's body before she becomes pregnant.

"What is methylmercury?"
It's a metal that can be found in certain fish, including swordfish, tilefish, king mackerel, and shark. Eating these fish can be harmful to your unborn baby.


"I'm not pregnant - so why should I be concerned about methylmercury?"
If you regularly eat the above types of fish, methylmercury can accumulate in your blood stream over time. It's removed from the body naturally, but it may take over a year to drop to a safe level. So if you happen to become pregnant during that time, methylmercury can pass from your blood into that of your unborn child.


"How could methylmercury affect my unborn baby?"
Some fish and shellfish contain higher levels of mercury that may harm an unborn baby or young child's developing nervous system.


"How would I know if I've been exposed to methylmercury?"
You will not show noticeable symptoms from eating commercial seafood, but your newborn may experience symptoms (see answer above). If you think you've been exposed to methylmercury, see your doctor or healthcare provider immediately.


"Does this mean I can't eat other types of fish?"
No, it's okay to eat other cooked fish/seafood as long as you select a variety of other kinds while you're trying to become pregnant or while you're pregnant. You can eat up to 12 ounces (2 average meals) a week of a variety of fish and shellfish that are lower in methylmercury. Five of the most commonly eaten fish and shellfish that are low in methylmercury are shrimp, canned light tuna, salmon, pollock, and catfish. Another commonly eaten fish, albacore ("white") tuna has more methylmercury than canned light tuna. So, when choosing your two meals of fish and shellfish, you may eat up to 6 ounces (one average meal) of albacore tuna per week. 


Follow these steps before you become pregnant to help keep your baby safe!

For more information, see Methylmercury in While You're Pregnant.

Note: If you think you've been exposed to methylmercury or have questions, see your doctor or healthcare provider immediately.


For information about food safety, call the FDA's Food Information Line at: 1-888-SAFE-FOOD.