Substances that may cause birth defects

You don't want any harm coming to your baby while you're pregnant, which is why it's very important that you know about teratogens. Simply put, teratogens are airborne or environmental substances that have the potential to cause birth defects. They range from viruses and bacteria to alcohol and certain chemicals.


Some viruses can have ill effects on the fetus if the mother-to-be becomes infected. The varicella virus is a teratogen that many mothers-to-be worry about, because chicken pox during pregnancy can be complicated and dangerous. Thankfully, chicken pox infection is rare, occurring in only about 1 out of every 2,000 pregnant women; 90 percent of pregnant women in the United States are immune to the varicella virus, which causes chicken pox. Chicken pox and pregnancy provides a good example of why you should be mindful of teratogens but not overly concerned or paranoid about them.

The rubella virus, like chicken pox, can be particularly dangerous during pregnancy, as it can lead to a condition known as congenital rubella syndrome in which the virus can harm the baby, particularly if contracted before pregnancy or during the first trimester of pregnancy. Toxoplasmosis, a parasitic disease which can be transmitted to humans from animals, can be extremely dangerous to pregnant women.

More Teratogens to Be Aware Of

Excessive alcohol consumption is another teratogen, with the potential to lead to low birth weight and a condition known as fetal alcohol syndrome. Lead poisoning poses similar dangers; be careful not to expose yourself to high levels of lead, and drink alcohol very sparingly if at all while you're pregnant. Ask your doctor about proper health and nutrition for pregnant women if you have any questions about what you should or should not eat, drink or expose yourself to.

Certain drugs are known to cause birth defects and are therefore considered teratogens as well. Isotretinoin or Accutane birth defects and finasteride or Propecia birth defects are both well-documented. Avoid both of these drugs if you are pregnant. Thalidomide, a sedative which is now used as an immune system modulating agent, is perhaps the most infamous pharmaceutical teratogen of all time. Thousands of babies around the world were born with missing or deformed limbs in the late 1950s and early 1960s, when it was prescribed to pregnant women to combat morning sickness.

To avoid teratogens, be cautious about environments you expose yourself to and always tell your doctor if you're pregnant, may be pregnant or may become pregnant before starting any new medications. When it comes to teratogens, the best treatment is prevention.