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Birth Defects

About Birth Defects

A birth defect is a problem that occurs when a baby is developing in utero (in the womb). Approximately 1 out of every 33 babies in the United States is born with a birth defect.

Birth defects can be minor or severe. They may affect appearance, organ function, or physical or mental development. Most birth defects are present within the first three months of pregnancy, when the organs are still forming. Some birth defects are harmless, while others require long-term medical treatment. Severe birth defects are the leading cause of infant death in the United States, accounting for 20 percent of deaths.

What Causes Birth Defects?

Birth defects can be a result of genetics, lifestyle choices and behaviors, exposure to certain medicines and chemicals, infections during pregnancy, or a combination of these factors. However, the exact causes of certain birth defects are often unknown.


The mother or father may pass on genetic abnormalities to their baby. Genetic abnormalities occur when a gene becomes flawed due to a mutation (change). In some cases, a gene or part of a gene might be missing. These defects happen at conception (fertilization) and often can’t be prevented. A particular defect may be present throughout the family history of one or both parents.

Nongenetic Causes

The causes of some birth defects can often be difficult or impossible to identify. However, certain behaviors greatly increase the risk of birth defects. These include smoking, using illegal drugs, and drinking alcohol while pregnant. Other factors, such as exposure to toxic chemicals or viruses, also increase risk.

What Are the Risk Factors for Birth Defects?

All pregnant women have some risk of delivering a child with a birth defect. Risk increases under any of the following conditions:

  • family history of birth defects or other genetic disorders
  • drug use, alcohol consumption, or smoking during pregnancy
  • advanced maternal age of 35 years or older
  • inadequate prenatal care
  • untreated viral or bacterial infections, including sexually transmitted infections
  • use of certain high-risk medications such as isotretinoin and lithium

Women with pre-existing medical conditions, such as diabetes, are also at a higher risk for having a child with a birth defect.

Common Birth Defects

There are more than 4,000 types of known birth defects. They’re typically classified as structural or functional/developmental. Structural defects are when a specific body part is missing or malformed. The most common structural defects are:

  • heart defects
  • cleft lip or palate (when there’s an opening or split in the lip or roof of the mouth)
  • spina bifida (when the spinal cord doesn’t develop properly)
  • clubfoot (when the foot points inward instead of forward)

Functional or developmental birth defects cause a body part or system to not work properly. These often cause disabilities of intelligence or development. Functional or developmental birth defects include metabolic defects, sensory problems, and nervous system problems. Metabolic defects cause problems with the baby’s body chemistry.

The most common types of functional or developmental birth defects include:

Some children experience physical problems associated with specific birth defects. However, many children show no visible abnormalities. Defects can sometimes go undetected for months or even years after the child is born.

How Are Birth Defects Diagnosed?

Many birth defects can be diagnosed during pregnancy, depending on the particular type of birth defect. Prenatal ultrasounds can be used to diagnose certain birth defects in utero. More in-depth screening options, such as blood tests and amniocentesis (taking a sample of the amniotic fluid), may also be done. These tests are usually offered to women who have higher risk pregnancies due to family history, advanced maternal age, or other known factors.

Prenatal tests can help determine whether the mother has an infection or other condition that’s harmful to the baby. A physical examination and hearing test may also be used to diagnose birth defects after the baby is born. A blood test called the newborn screen can help diagnose some birth defects shortly after birth, before symptoms occur.

It’s important to know that prenatal screening doesn’t always find defects when they’re present. A screening test can also falsely identify defects. Most birth defects can be diagnosed with certainty after birth.

How Are Birth Defects Treated?

Treatment options vary depending on the condition and level of severity. Some birth defects can be corrected before or shortly after birth. Other defects, however, may affect a child for the rest of their life. Severe birth defects, such as cerebral palsy or spina bifida, can cause long-term disability or death. Mild defects can be stressful, but they don’t typically affect overall quality of life. Speak with your doctor about the appropriate treatment for your child’s condition.


Medications may be used to treat some birth defects or to lower the risk of complications from certain defects. In some cases, medication may be prescribed to the mother to help correct an abnormality before birth.


Surgery can be done to fix certain defects or ease harmful symptoms. Some people with physical birth defects, such as cleft lip, may undergo plastic surgery for either health or cosmetic benefits. Many babies with heart defects will need surgery.

Home Care

Parents may be instructed to follow specific instructions for feeding, bathing, and monitoring an infant with a birth defect.

How Can Birth Defects Be Prevented?

Many birth defects can’t be prevented, but there are some ways to lower the risk of having a baby with a birth defect. Women who plan on becoming pregnant should start taking folic acid supplements before conception. These supplements should also be taken throughout the pregnancy. Folic acid can help prevent defects of the spine and brain. Prenatal vitamins are also recommended during pregnancy.

Women should avoid alcohol, drugs, and tobacco during and after pregnancy. They should also use caution when taking certain medications and getting vaccinated. Some medications and vaccines that are normally safe can cause serious birth defects when taken by pregnant women. Make sure to tell your doctor about any medications (including over-the-counter drugs and supplements) you may be taking. You should also ask them which vaccines are necessary and safe.

Maintaining a healthy weight also helps reduce the risk of complications during pregnancy. Women with pre-existing conditions, such as diabetes, should take special care to manage their health.

It’s extremely important to attend regular prenatal appointments. Additional prenatal screening can be done to identify defects if your pregnancy is considered high risk. Depending on the type of defect, it may be able to be treated before the baby is born.

Genetic Counseling

A genetic counselor can advise couples with family histories of or other risks factors for birth defects. A counselor may be helpful when you’re thinking about having children or already expecting. Genetic counselors can determine the likelihood that your baby will be born with defects by evaluating family history and medical records. They may also order tests to analyze the genes of the mother, father, and baby.

Content licensed from:

Written by: the Healthline Editorial Team
Published on: Jul 25, 2012
Medically reviewed on: May 26, 2017: Karen Gill, MD

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
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