What to Know About Teratogens and Birth Defects

Medically Reviewed by Dan Brennan, MD on August 20, 2022
5 min read

If you’re looking to become pregnant or are already pregnant, then you may have heard about teratogens and how they’re associated with certain birth defects. Here is some important information concerning teratogens and how they affect pregnancy. 

A teratogen is an environmental factor that a person is exposed to during their pregnancy that may affect the baby’s development, resulting in birth defects. In fact, around 4% to 5% of birth defects are the result of teratogen exposure. 

Once the baby has developed and a blood supply connection has formed between them and the pregnant person, anything that the pregnant person is exposed to, including teratogens, can transfer to the baby and affect their development. Due to this, it is believed that teratogens can affect the baby anywhere from 10 to 14 days after conception. 

There are several common types of teratogens that can harm a child’s development and result in birth defects. Examples of these teratogens include:

  • Certain medications 
  • Recreational drugs 
  • Alcohol
  • Tobacco 
  • Toxic chemicals
  • Certain bacteria and viruses 
  • Certain health conditions 

It should be noted, though, that not all chemicals and medications cause harm to your child or pregnancy. These agents are known as nonteratogenic and have no known association with birth defects. These nonteratogenic agents include:

  • Spermicides such as birth controls, gels, creams, foams, and condoms 
  • Acetaminophen, such as that found in common pain medications 
  • Prenatal vitamins that have been prescribed to pregnant people 
  • Microwave ovens that emit nonionizing radiation 

Teratogens are classified using the following categories: 

  • Physical agents, which include ionizing agents, hyperthermia, and more
  • Chemical agents, such as organic mercury compounds, herbicides, industrial solvents, and more
  • Infectious agents, like rubella, herpes simplex, syphilis, and more
  • Maternal health conditions, including maternal PKU, diabetes, and more

These teratogens can be found in your homes or in workplaces. Pregnant people are most vulnerable to these exposures during their first half of pregnancy. Depending on the genetics of the pregnant person and their baby, exposures can cause varying levels of abnormalities.

Physical agents

Some physical agents can lead to hyperthermia, which is linked to neural tube defects and cardiovascular abnormalities. Evidence also shows an association between pregnant people who tested with a high fever and congenital abnormalities, abdominal wall defects, or Hirschsprung disease in their babies.

Chemical agents

Chemical agents like alcohol and smoking are some of the most preventable causes of birth defects or disabilities. In some cases, prenatal exposure to alcohol can affect the baby in the first 3 to 8 weeks, which is oftentimes before the pregnant person even knows they are pregnant. A group of abnormalities caused by alcohol consumption is classified as fetal alcohol syndrome, which may lead to mental retardation.

Infectious agents

Infectious agents like rubella, syphilis, herpes, etc. can also cause potential birth defects. They have been linked to congenital malformation in the baby. A pregnant person may become infected after drinking contaminated water, consuming contaminated meat, or touching infected cat feces.

Maternal conditions

Maternal conditions that affect a pregnant person can include diabetes, malnutrition, and thyroid conditions. Hypoglycemia may occur during pregnancy, which could cause fetal malformations. Studies also show the risk of baby malformations rises from 4% to 10% in the babies of pregnant people who have diabetes during pregnancy. Gestational diabetes may also cause high blood sugar levels, which have been linked to neural tube, brain, and spinal cord defects. 

If the pregnant person suffers from thyroid disorders, that may also affect a baby's development during pregnancy.

While not all birth defects can be prevented or avoided, there are certain measures you can take in order to help prevent certain birth defects in certain situations.

These preventive measures include:

  • Prenatal care: A daily prenatal vitamin consisting of at least 400 micrograms of folic acid should be consumed. This type of prenatal vitamin can help prevent a number of birth defects. Prenatal vitamins should be taken as soon as you find out you’re pregnant but can also be taken once you’re at the age of reproduction or once you have started to try and conceive. 
  • Avoid certain substances: Substances such as alcohol, tobacco, and recreational drugs should be avoided upon learning that you are pregnant. Not only can these substances cause birth defects, but they can also cause complications during pregnancy. Avoiding them as soon as you find out you’re pregnant or even before will help prevent these situations from occurring. 
  • Consider current and past medical conditions: Current and past medical conditions, infections, and diseases should be taken into consideration. Some diseases and genetic factors can contribute to birth defects. In addition, if you had a pregnancy in the past that had a birth defect, it’s important to try and figure out what caused the defect so that you can come up with a preventive plan with your physician before becoming pregnant again.

While not all birth defects can be detected during pregnancy, it’s still important to get regular screenings to ensure that your baby is healthy. Certified prenatal ultrasound groups can also conduct high-resolution ultrasounds in order to detect defects prior to birth, especially defects that may cause significant impairment to your child. 

Some birth defects can be treated while the baby is still in utero, and it’s important to try and correct those defects before the baby is born. By treating these defects in utero, you can hope to correct damages done to vital organs. 

Two birth defects that can be treated in utero include:

  • Congenital diaphragmatic hernia: This condition happens when a hole in the diaphragm restricts lung development due to abdominal content entering the chest through the hole. A surgery known as fetoscopic endotracheal occlusion is performed to increase lung function and improve survival rates. 
  • Lower urinary tract obstruction: This condition occurs when the baby’s urine flow is obstructed and unable to exit the baby’s body. This can result in permanent kidney damage, but getting rid of the obstruction prior to birth can protect the kidneys.

In addition to these two defects, there are also other conditions that can be treated while the baby is still in utero. For example, if your baby has an irregular heartbeat, medication can be administered in order to treat your child.