Mercury and pregnancy

Pregnant woman staring at her belly

Mercury is a metal. If you come in contact with high levels of mercury during pregnancy, it can cause real problems for you and your baby.

Mercury can damage many parts of your body, including your lungs, kidneys and nervous system (that includes the brain, spinal cord and nerves). It also can cause hearing and vision problems. How serious the damage is depends on how much mercury you’re exposed to. Babies exposed to mercury in the womb can have brain damage and hearing and vision problems.

How can you be exposed to mercury?

Mercury has several forms:

  • It can be a colorless, odorless, poisonous vapor in the air. It’s released into the air when it’s spilled or when something that contains it breaks. It’s also released through industrial processes, like burning waste or burning coal in power plants.
  • It can fall from the air back to earth and build up in oceans, lakes, rivers and streams. Fish get mercury from the water they swim in and from eating other fish that have mercury in them.
  • It’s a shiny, silver-colored substance used to make dental fillings, fever thermometers and other products.

You can be exposed to mercury through:

  • Your skin, by touching it
  • The air, by breathing it in
  • Eating or drinking food or water contaminated with it

How can you keep yourself safe from mercury? 

Here’s what you can do:

  • Don’t eat fish that contain high amounts of mercury. These include shark, swordfish, king mackerel and tilefish.
  • If you need to get a filling, ask your dentist about filling options. You may be able to have a filling that doesn’t contain mercury. Don’t have any mercury fillings removed unless they’re broken or damaged. Be sure your dentist knows you’re pregnant before you have any dental work done.
  • Don’t use a vacuum cleaner to clean spilled mercury.
  • Ask an adult who’s not pregnant to throw away any broken thermometers or fluorescent light bulbs. Store these items in a way that prevents them from breaking, and don’t let children use them.
  • If you may be exposed to mercury at your job (like in a dentist’s office or do electrical, chemical or mining work), talk to your boss about safety precautions. For example, you may work in a dentist’s office, do electrical, chemical or mining work, or use mercury to make products. Ask if you can switch to a different position or task during pregnancy

Talk to your health care provider about protecting yourself from mercury.

What is methylmercury?

Methylmercury is made when mercury in the air gets into water. The mercury in the air comes from natural sources (such as volcanoes) and man-made sources (such as burning coal and other pollution).

You can get methylmercury in your body by eating fish that contain a lot of mercury. These fish get mercury from the water they swim in and from eating other fish that have mercury in them. Mercury is mostly found in large fish, like swordfish, shark, king mackerel and tilefish. During pregnancy, don’t eat these kinds of fish because the mercury in them can harm your baby.

During pregnancy, eat 8 to 12 ounces each week of fish that are low in mercury, like shrimp, salmon, pollock, catfish and canned light tuna. It’s OK to eat 6 ounces a week of albacore (white) tuna.  

What is elemental mercury?

Elemental mercury (also called pure mercury) is a shiny, silver-colored substance. When it’s spilled or something that contains it breaks, the mercury becomes an invisible, odorless and poisonous in the air. Elemental mercury may be found in:

  • Dental fillings made from amalgam. Amalgam contains elemental mercury, silver and other metals. Small amounts of mercury from these fillings can get into the air you breathe. Amalgam fillings are safe for adults and children over age 6. But we don’t know their effects on pregnant women. If you’re worried about having an amalgam filling, talk to your dentist or health care provider.
  • Fever thermometers. Mercury in fever thermometers is surrounded by glass. It’s not harmful unless the glass breaks and you touch the mercury or it gets into the air you breathe. If you break a thermometer, don’t vacuum the spilled mercury. Instead, use a piece of paper to roll the beads of mercury onto another piece of paper. Seal the paper in a plastic bag. Contact your local health department to ask how to throw the mercury away.
  • Some antiques, like clocks, barometers and mirrors.
  • Some button cell batteries, like watch batteries. Most batteries made in the United States don’t contain mercury.
  • Some jewelry, especially glass pendants made outside the United States
  • Skin-lightening creams made outside the United States

If you’re worried about being exposed to elemental mercury, talk to your health care provider.

Last reviewed June 2014