A Short Summary of Congenital Malformations & Teratogenic Agents

Expectant parents: this is important for you (and for your future child)!

In short: a congenital malformation is an anatomical or structural abnormality present at birth. Congenital malformations may be caused by genetic factors, environmental insults, or a combination of the two during prenatal development.

Most common congenital malformations demonstrate multifactorial inheritance with a threshold effect and are determined by a combination of genetic and environmental factors.

During the first two weeks of gestation, teratogenic agents usually kill the embryo rather than cause congenital malformations. Major malformations are more common in early embryos than in newborns; however, most severely affected embryos are spontaneously aborted during the first six to eight weeks of gestation. During organogenesis between days 15 to 60, teratogenic agents are more likely to cause major congenital malformations.

What is a Teratogen?

A teratogen is any agent that causes an abnormality following fetal exposure during pregnancy.

Teratogenic Agents

Here is a list of most common teratogenic agents:

• Drugs used in Hypertension
  ACE inhibitors are relatively safe in the 1st trimester but can have severe effects in the 2nd and 3rd trimesters. Statins are also teratogenic and should be stopped at least three months before conception.
• Anti-epilepsy Drugs
  Unfortunately, most AEDs are teratogenic; however, the risk is reduced with monotherapy. The risk to the fetus needs to be balanced with the severity and frequency of seizures.
• Alcohol
  No safe threshold is defined for pregnant women, so the best way to protect yourself from possible risks is not to consume alcohol during pregnancy.
• Vitamin A
  High doses of Vitamin A may cause the malformation of the ear.
• Antibiotic
  Some antibiotics like penicillins, erythromycin, and cephalosporins are safe, but you should avoid streptomycin (3rd trimester), tetracycline family, and trimethoprim (1st trimester).
• Warfarin
  Pregnant women should avoid it in the 1st trimester.
• Lithium
  Lithium should avoid by pregnant women throughout the pregnancy.
• Drugs
  All kinds of drugs must be avoided throughout the pregnancy.
• Infections
  Some infections like Rubella, Cytomegalovirus, Varicella, and Herpes Simplex may have teratogenic effects.
• Illnesses of the mother
  Some illnesses like Insulin-dependent diabetes (juvenile diabetes), Phenylketonuria, Iodine deficiency may have teratogenic effects.
• Radiation
  Must be avoided from exposure to UV and Ionising radiations throughout pregnancy.

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