What is a teratogen?

A teratogen is anything a woman is exposed to during pregnancy that can harm her unborn baby (fetus). Teratogens can be things that she breathes in, swallows, or touches.

Exposure to a teratogen can cause a birth defect in the unborn baby. A teratogen may also result in the death of an unborn baby. Not all birth defects are obvious at birth. Sometimes the birth defect may not be identified until later in life, such as when a child starts school.

Did you know alcohol is a teratogen?

How does a teratogen reach the fetus?

The placenta and umbilical cord attach the mother’s uterus to the fetus. Blood travels from the mother to the fetus and back to the mother through the placenta and umbilical cord. There are good things in the mother’s blood, such as oxygen and food, for the fetus. However, when a mother is exposed to a teratogen, her blood can also carry bad things to the fetus.

The human body is made up of hundreds of cells. When a fetus is growing, cells are dividing quickly to allow for the development of the human body, such as the brain, heart, legs, and ears. A teratogen can cause these dividing cells to die or change. This affects the normal growth of the fetus.

The fetus develops during all 9 months of pregnancy. Parts of the human body develop at different times during pregnancy. For example, the heart develops from week 5 to week 11, and the teeth develop from week 8 to week 40. When a pregnant woman is exposed to a teratogen, the body parts of the fetus that are developing at that time may be harmed.

The fetus’s brain is very sensitive to teratogens as it is the only organ that is developing for all 9 months of pregnancy.

Why is alcohol a teratogen?

Alcohol can harm, or change, an unborn baby’s growing cells at any time during pregnancy. These changes can result in physical, emotional, learning, social, and behavioural concerns. Since the brain develops through all 9 months of pregnancy, whichever part of the brain is developing at the time of exposure may be harmed. Often the effects of this harm are not known until the child is in school.

Are some types of alcohol safer than other types?

Any type of alcohol can harm a baby. This includes the alcohol found in:

  • Wine
  • Beer
  • Coolers
  • Hard liquors
  • Liqueurs
  • Hairspray
  • Mouthwash
  • Lysol
  • Hand sanitizer
Why aren’t all fetuses who are exposed to alcohol harmed?

The impact that alcohol has is different for each fetus. Alcohol’s effect on the unborn baby is influenced by things such as:

  • When, during pregnancy, the fetus is exposed to alcohol
  • How much alcohol is used (e.g., 1 drink, several drinks at a time)
  • The pattern of drinking (e.g., once in pregnancy, daily)
  • What the mother has been eating and drinking
  • The mother’s and father’s genetics

It’s never too late to say, “No thanks” to alcohol. Good nutrition, reduced stress, caring relationships, regular medical care, and avoiding alcohol and drugs during pregnancy help unborn babies to develop in a healthy way.

Do you need help to stop drinking?

If you want to stop drinking, talk to:

  • Your doctor or healthcare provider
  • Addictions services in your area
  • First Nations and Inuit Hope for Wellness Help Line 1-855-242-3310

For more information on teratogens, you can go to: www.mothertobaby.org and www.aboutkidshealth.ca.

For information on pregnancy and alcohol, you can go to: www.skprevention.ca/alcohol. To order teratogen resources you can go to:

A teratogen is NOT a dinosaur is adapted with permission from Foothills Fetal Alcohol Society.


Berk, L. E. & Shanker, S. G. (2006). Child development (2nd ed.). Toronto, ON: Pearson Education.

Bilotta, J., Barnett, J. A., Hancock, L., & Saszik. (2004). Ethanol exposure alters zebrafish development: A novel model of fetal alcohol syndrome. Neurotoxicology and Teratology, 26 (6):737-43. doi: 10.1016/j.ntt.2004.06.011

Brigg, G. G., Freeman, R. K., & Yaffe, S. J. (2011). Drugs in pregnancy and lactation: a reference guide to fetal and neonatal risk (9th ed.). Philadelphia, PA: Lippincott Williams & Wilkins.

Stratton, K., Howe, C., & Battaglia, F. (1996). Fetal Alcohol Syndrome: Diagnosis, Epidemiology, Prevention, and Treatment. Washington, DC: Institute of Medicine, National Academy Press. www.nap.edu/read/4991/chapter/1

Saskatchewan Prevention Institute