Health Library

What Is a Birth Defect?

A birth defect is a problem with how a baby’s body parts form or how they work. The baby is born with the problem, but it might not be recognized until later. Sometimes the problem is inherited (passed down in families). Often the cause is not known.

Some birth defects (also called congenital disorders or congenital anomalies) are mild and don’t need any treatment. Others can be serious and require lifelong treatment.

What Types of Birth Defects Are There?

There are many types of birth defects such as:

• heart problems such as hypoplastic left heart syndrome, transposition of the great arteries, and tetralogy of Fallot
• spina bifida
• orofacial cleft
• clubfoot 
• Down syndrome
• hemophilia
• congenital dislocated hip
• Tay-Sachs disease 
• phenylketonuria (PKU), which affects the way the body processes protein
• fetal alcohol syndrome

How Are Birth Defects Diagnosed?

Birth defects usually are found through genetic testing done on small samples of blood or saliva (spit). Tests can be done before a baby is born, right after the birth (such as newborn screening), or later.

During pregnancy, genetic testing can also be done on amniotic fluid (through amniocentesis) or the placenta (through chorionic villus sampling). Genetic testing can also be done as a part of in vitro fertilization (IVF). The embryo can be tested before it is put into the uterus.

Prenatal Testing

Prenatal tests are done before the baby is born. During routine prenatal care, blood tests and ultrasounds are done to see if a baby could have a birth defect. If the results are concerning, parents may decide to have more testing.

Newborn Screening

Newborn screening tests on babies look for some kinds of health problems. These conditions are treatable, so it’s important to find them right away. With the parents’ permission, the baby is tested for PKU, congenital hypothyroidism, sickle cell disease, and about 30 other conditions.

Other Testing

Sometimes a birth defect isn’t diagnosed during pregnancy or with newborn screening. If a genetic illnesses run in the family or if a baby has symptoms of a genetic illness, parents may decide to get more testing. A genetic counselor can help parents decide what tests would be helpful.

Why Do Birth Defects Happen?

The cause of most of these health problems isn’t known. Some are inherited while others are not. Other causes include:

• a change in the baby’s genes, such as a mutation or extra chromosomes
• some types of medicines taken during pregnancy
• smoking, alcohol, or drug use during pregnancy
• infections during pregnancy (for example, toxoplasmosis or chickenpox)
• chemical exposure during pregnancy (for example, to lead or mercury)

What Can Help Prevent Birth Defects?

Parents can take steps before and during a pregnancy to help lower the risk of birth defects in newborns, such as:

• taking folic acid supplements
• making sure they don’t have any sexually transmitted diseases (STDs)
• getting all recommended immunizations
• only taking medicines that are absolutely needed and that the health care provider says are OK
• avoiding alcohol and drugs
• not smoking and avoiding secondhand smoke

How Can Parents Help?

If your child is born with a birth defect:

Acknowledge your emotions. You might feel shock, denial, grief, and even anger. Accept those feelings, and talk about them with your spouse/partner and other family members. You also might consider talking to a social worker, counselor, or psychologist.

Celebrate your child. Let yourself enjoy your baby the same way any new parent would — by cuddling and playing, watching for developmental milestones (even if they’re different from those in other children), and sharing your joy with family members and friends. Some parents wonder if they should send birth announcements. This is a personal decision — the fact that your baby has a health problem doesn’t mean you shouldn’t be excited about the new addition to your family.

Learn all you can and get support. Understanding your child’s condition can help you get them the best care possible. Go to your child’s doctors and care team with any questions. Talking with someone who’s been through the same thing also can help. Consider joining a support group — look online or ask your health care provider or a social worker about local groups.

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