Mercury and PCBs in Fish: A Pregnancy Health Hazard?

Now that you are pregnant, you are probably very concerned about maintaining a healthy diet. The nutrition that comes from a well-balanced diet can prove invaluable to both you and your baby throughout pregnancy. But lately, you may have heard quite a bit about the hazards of eating fish while pregnant. Fish can contain high levels of mercury and PCBs, which can pose health hazards to a developing fetus. But should you cut out fish completely during your pregnancy, or is fish still an important part of any pregnancy diet?

A Fishy Subject
We all know that fish can be a very nutritious part of our daily diet. Fish is low in fat, high in protein, and contains many essential vitamins and nutrients. For those who don’t eat red meat, fish can also help to supplement intake of iron and protein, which is necessary for a growing baby. But fish can also be high in things that are not so good for you, especially during pregnancy. Because they are swimming around in polluted lakes, rivers, and oceans, sometimes our fish can actually be quite toxic.

Mercury and Fish
Fish often contain high levels of mercury in their body tissues. Mercury is an element that occurs naturally in the air, soil, and water. It comes in a variety of different forms and is often used to make products like thermometers and light bulbs. Mercury is also given off during certain production processes, like coal burning, chlorine production, and the disposal of hazardous wastes.

Fish contain high levels of a special type of mercury, called methylmercury. Methylmercury is highly toxic, and leaches into fish through the water that they swim in. Many fish also consume mercury when they prey on the other fish around them. Over time, methylmercury builds up in a fish’s body, meaning that the older and larger the fish is, the more mercury he probably has in his system. Large predators, like sharks, grouper, and swordfish tend to contain very high levels of methylmercury.

The Dangers of Mercury
Though you may not realize it, when you eat fish you are actually ingesting the mercury that the fish is contaminated with. If you eat a lot of mercury-contaminated fish, you could end up suffering some severe consequences. Unfortunately, this mercury can also affect your developing baby. High levels of mercury can affect the development of both your baby’s brain and nervous system.

PCBs and Fish
In addition to mercury, most fish also contain some levels of PCBs in their system. PCBs, or polycarbonated biphenyls, are made up of synthetic and organic chemicals. PCBs are used in hundreds of different commercial and industrial applications, and, unfortunately, have polluted our air, soil, and waterways.

PCBs are generally found in larger fish, but is actually pretty hard to tell which fish are the worst offenders. Depending upon where you live and what the water quality is like in your area, different fish can have different PCB levels. Common offenders are freshwater sport fish like big mouth and small mouth bass.

PCBs are also particularly bad for your health. They have been associated with immune system and neurological disorders. PCBs are especially harmful for pregnant women. They have been associated with a number of fetal development problems including:

Should You Avoid Fish During Pregnancy?
Without a doubt there are a few types of fish that you should avoid completely during pregnancy because of their mercury and PCB levels. These include:

  • tilefish
  • king mackerel
  • shark
  • swordfish

However, it is important not to cut out all fish from your diet. Research has shown that avoiding all fish during pregnancy might be harmful to your baby. A recent study performed at Harvard suggests that women who consume more fish have children who perform higher on early cognitive tests. This is because fish contains high amounts of a special nutrient, called Omega-3 essential fatty acid. Omega 3 has been found to be very beneficial during pregnancy as it helps:

  • promote brain development
  • prevent heart disease
  • promote bone health

The general consensus seems to be that pregnant women should focus on eating at least two servings per week of fish that are low in mercury and PCBs.

Fish to Consume
So what fish should you concentrate on eating? Well, you want to find fish that are low in mercury and PCBs. Fish that are low in mercury include:

  • shrimp
  • canned tuna (light)
  • salmon
  • catfish

You can eat up to 12 ounces per week of these fish without having to worry about your mercury intake. If you choose albacore tuna though, limit yourself to only six ounces, because it is slightly higher in mercury. Fish that are low in PCBs tend to be smaller and younger, but contact your environmental agency for the specific types of fish that are safe to eat in your area.

Concerned about your pregnancy diet? Visit our forum to talk with other moms-to-be

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