Before You Become Pregnant
Some fish and shellfish contain high levels of methylmercury, which can harm an unborn child's developing nervous system, even before conception. Fish in the diet is the major source of methylmercury.

Nearly all fish contain traces of methylmercury, but larger fish that have lived longer have the highest levels of methylmercury because they have had more time to accumulate it. These large fish pose the greatest risk to pregnant women who eat them regularly.

What is Methylmercury?
Methylmercury is a metal that can be found in certain fish. Eating these fish can be harmful to your unborn baby. Women who are trying to become pregnant, are pregnant, or nursing mothers and young children should not eat the following fish, as they can contain high levels of methylmercury:

• Swordfish
• Tilefish
• King mackerel
• Shark

Mercury occurs naturally in the environment and can also be released into the air through industrial pollution. It falls from the air and can get into surface water, accumulating in streams and oceans. Bacteria in the water cause chemical changes that transform mercury into methylmercury, which can be toxic. Fish absorb methylmercury as they feed on aquatic organisms.

Methylmercury can build up in a woman's body before she becomes pregnant. If you are thinking about becoming pregnant, you should be aware of these risks and take steps to prevent exposure to methylmercury.

If you regularly eat the above types of fish, methylmercury can accumulate in your blood stream over time. Methylmercury is removed from the body naturally, but methylmercury may take over a year to drop to a safe level. If you happen to become pregnant during that time, methylmercury can pass from your blood into that of your unborn child.

It's okay to eat other cooked fish/seafood as long as you select a variety of other kinds while you are trying to become pregnant or while you are pregnant.

You can eat up to 12 ounces (2 average meals) a week of a variety of fish and shellfish that are lower in mercury.

Five of the most commonly eaten fish that are low in mercury are:

• Shrimp
• Canned light tuna
• Salmon
• Pollock
• Catfish

Another commonly eaten fish, albacore ("white") tuna has more mercury 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!

Note: If you think you've been exposed to methylmercury or have questions, see your doctor immediately.
Source: www.fda.gov