Medical Genetics: Teratogens
What is a teratogen?
A teratogen is something that can cause or raise the risk for a birth defect in a
baby. They are things that a mother may be exposed to during her pregnancy. Teratogens
How to say it
The riskiest times of pregnancy
Experts believe that teratogens can begin affecting a baby growing in the womb about
10 to14 days after conception. Conception is when a woman’s egg is fertilized by a
man’s sperm. After conception, it takes about 6 to 9 days for the egg to implant in
the uterus. Once the fertilized egg is attached to the uterus, the mother and the
embryo share a blood supply. Chemicals in the mother's blood can then affect the growing
As a baby grows in the womb, teratogens may affect parts of the baby’s body as they
are forming. For example, the neural tube closes in the first 3 to 5 weeks of the
pregnancy. During this time, teratogens can cause neural tube defects such as spina
bifida. Some organs are sensitive to teratogens during the whole pregnancy. This includes
the baby's brain and spinal cord. Alcohol affects the brain and spinal cord, so it
can cause harm at any time during pregnancy. This is why you should not drink alcohol
if you are pregnant.
How are teratogens known?
Researchers have two ways of finding out if a substance is a teratogen. They are:
Animal studies. Animal studies are the main way to find out if a medicine or other substance is safe
during human pregnancy.
Observations from human exposure. This means reports of problems about a substance over time.
What are nonteratogenic agents?
Certain things have been shown to not cause birth defects. These are called nonteratogenic
agents. These include:
Spermicides. These are chemicals that kill sperm to prevent pregnancy. These chemicals are found
in products for birth control, such as gels, creams, and foams, and on some condoms.
Studies have shown no link with the use of spermicides and any increased chance for
Acetaminophen. This is a common ingredient in some pain medicines. There has been no link between
birth defects and taking acetaminophen at the advised dose during pregnancy.
Prenatal vitamins. Prenatal vitamins are prescribed to pregnant women to help meet the extra nutritional
needs of pregnancy. When used at the recommended dose, they don’t increase the risk
for birth defects. But don’t take any extra vitamins, minerals, or herbal supplements
without talking with your healthcare provider first. Extra amounts may be harmful.
Microwave ovens. Microwave ovens use nonionizing radiation. This type of radiation is not teratogenic.
Microwaving food while pregnant is not known to increase the risk for birth defects
or health problems.
Talking with your healthcare provider
If you’re pregnant, talk with your healthcare provider about things to avoid during
pregnancy that may cause birth defects. They can answer your questions and help you
have a safe pregnancy.