Birth Defects

Minimize your risk of common birth defects

While pregnancy is a time of joy and expectation, it can also be a time of great worry. Many expectant parents can't help worrying that something might go wrong with the pregnancy, and this point often seems to be driven home by the myriad routine tests and screenings recommended by obstetricians. While the majority of babies born do turn out to be perfectly normal, the CDC reports that as many as 1 in 33 newborns in the United States have birth defects. These can range from relatively minor to very serious.

Birth defects (also known as congenital anomalies) are abnormalities of structure or function present at birth. Many birth defects may lead to physical or mental disability. Some may even be fatal, and in fact birth defects are the leading cause of death in first year of life.


A structural defect is one in which a body part is missing or incorrectly formed, such as a congenital heart defect. A functional defect refers to a problem with the way a body part or system works. Metabolic defects such as phenylketonurea (PKU) are examples of this second type. In PKU, the body does not produce an enzyme necessary for breaking down proteins.

Causes of Birth Defects

Birth defects can be caused by genetic or environmental factors, or combination of the two, but many birth defects simply aren't understood. According to the March of Dimes, 60 percent of the time the cause of the birth defect is unknown.

Some birth defects are genetic. They may either be inherited from a parent, such as cystic fibrosis, or they may stem from an error occurring during fertilization, such as Down syndrome.

Other birth defects result from the mother's exposure to a harmful substance during her pregnancy. These are referred to as environmental birth defects. For example, alcohol, certain prescription medications and lead exposure can all cause congenital anomalies.

Congenital infections can also cause birth defects. These are infections that are passed from the mother to the fetus, either through the placenta or as the baby passes through the birth canal. Rubella, cytomegalovirus, toxoplasmosis and group B strep are all examples of infections that can endanger a fetus or newborn.

Common Birth Defects

There are thousands of known birth defects, but most are exceedingly rare. Here are some of the more commonly occurring birth defects in the United States, with their approximate rates of incidence:

  • Congenital heart defects occur in 1 out of 150 births.
  • Cerebral palsy occurs in 1 out of 500 births.
  • Cleft lip and/or cleft palate occur in 1 out of 700 births.
  • Down syndrome occurs in 1 out of 800 births.
  • Clubfoot occurs in 1 out of 1000 births.
  • Congenital hip dysplasia occurs in 1 out of 1000 births.
  • Neural tube defects occur in 1 out of 1000 pregnancies.

Birth Defect Prevention

Not all birth defects can be prevented, but there are steps you can take to reduce your risks. Talk to your doctor before you get pregnant about optimizing your health. Discuss any risk factors you may have and what can be done to mitigate those risks. During pregnancy take prenatal vitamins, eat healthy food and get plenty of rest and exercise. Above all, avoid smoking and alcohol, and talk to your doctor before taking any drugs or supplements. Many prescription drugs and even herbal supplements can be harmful in pregnancy.

Your doctor will offer you several opportunities for prenatal tests and screens during your pregnancy. Some of these check for conditions or infections in the mother which can then quickly be treated to prevent harm to the fetus. Others detect possible abnormalities in the developing fetus.

Once the baby is born, routine postnatal screening tests are performed to check for many possible defects so treatment can start right away, giving your infant the best chance at good health.