Definition - What does Teratogen mean?

A teratogen is any substance, chemical, medication, or even infection that causes abnormalities in the development of a fetus or embryo. Exposure to a teratogen during pregnancy may cause birth defects or it may outright terminate a pregnancy. A teratogen could be a street drug, alcohol, cigarette, or a disease in the mother that interferes with normal fetal development. Exposure to a teratogenic agent may account for 4% to 5% of birth defects. A well-known example of a teratogen is thalidomide – a medication which when used during the early stages of pregnancy resulted in cases of phocomelia, which is a birth defect in which the hands and feet are attached to the chest due to underdeveloped or absent arms and legs.

FertilitySmarts explains Teratogen

Teratogens are capable of crossing the placenta from the mother’s bloodstream and exerting their effects on the fetus. The effects of a teratogen depend on the type of agent, dose, and duration of use, and timing of exposure. The fetus is most vulnerable to teratogenic agents during the first half of pregnancy when the limbs and organs are developing.

The mother’s and fetus’s genetic makeup may also help predict the effects of certain teratogens.

There is an extensive list of substances that can cause birth defects in the fetus if taken during pregnancy; some of the important ones are as follows:

  1. Alcohol: Birth defects can occur following exposure to alcohol during in the first three to eight weeks of pregnancy. The body of a fetus processes alcohol very slowly than that of an adult. Thus, alcohol tends to stay in the baby’s blood for a longer period and prevents the nutrients and oxygen from reaching the developing organs. Women who consume alcohol during pregnancy are at risk of developing fetal alcohol syndrome (FAS). It is a spectrum of disorders characterized by several birth defects like facial and limb abnormalities as well as mental and speech delays. In particular, FAS is the most common non-inherited cause of developmental delays in the U.S.
  2. Cigarette smoking during pregnancy interferes with the growth of the developing fetus. It can also cause a baby to be delivered prematurely. Hence, women who smoke are prone to have low birth-weight babies. These babies can also experience several health issues during the newborn period, lifelong disabilities (e.g. developmental delays) and even death. Also noted, is a possible link between fetal smoking exposure and behavioral health problems in later childhood and teenage years.
  3. Medications used to treat epilepsy/seizures such as phenytoin and valproic acid. These medicines can cause heart abnormalities, cleft palate, and microcephaly (small-sized brain).
  4. Street drugs like marijuana, heroine, and cocaine

Teratogenic infections that vertically cross the placenta from the mother to the fetus, are best remembered as TORCHES:

  1. TToxoplasmosis
  2. OOther infections
  3. RRubella
  4. CCytomegalovirus, Chickenpox
  5. HHerpes simplex, Hepatitis B and C, HIV
  6. EEverything else sexually transmitted (gonorrhea, Chlamydia, human papillomavirus)
  7. SSyphilis
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