Begin Main Content Area

Birth Defects

According to the Centers for Disease Control and Prevention (CDC) birth defects affect about one in every 33 babies born in the United States each year. They are the leading cause of infant deaths, accounting for more than 20% of all infant deaths. Babies born with birth defects have a greater chance of illness and long term disability than babies without birth defects.

A birth defect is an irregularity of structure, function or metabolism (body chemistry) present at birth that results in a physical or mental disability, or which may cause death. Several thousand different birth defects have been identified; however, the causes of about 70% of birth defects are unknown.

Causes and Risk Factors

Birth defects occur before a baby is born. Most birth defects occur in the first 3 months of pregnancy, when the organs of the baby are forming. This is a very important stage of development. However, some birth defects occur later in pregnancy. During the last six months of pregnancy, the tissues and organs continue to grow and develop.

Most birth defects are thought to be caused by a complex mix of factors. These factors include our genes, our behaviors, and things in the environment. For some birth defects, we know the cause. But for most, we don't.

We do know that some women have a higher chance of having a child with a birth defect:

  • Women who take certain drugs, smoke, or drink alcohol during pregnancy.
  • Women with certain medical conditions, such as diabetes or obesity.
  • Women who take certain medications that are known to cause birth defects, such as isotretinoin (a drug used to treat severe acne).
  • Women who have someone in their family with a birth defect. To learn more about your risk of having a baby with a birth defect, you can talk with a clinical geneticist or a genetic counselor.
  • Women over the age of 35 years.

Learn about CDC's research on causes and risk factors.


Some birth defects can be prevented. There are things that a woman can do before and during pregnancy to increase her chance of having a healthy baby:

  • Take 400 mcg of folic acid every day, starting at least one month before getting pregnant.
  • Don't drink alcohol, smoke, or use "street" drugs.
  • Talk to a health care provider about taking any medications, including prescription and over-the-counter medications and dietary or herbal supplements. Also talk to a doctor before stopping any medications that are needed to treat health conditions.
  • Learn how to prevent infections during pregnancy.
  • If possible, be sure any medical conditions are under control, before becoming pregnant. Some conditions that increase the risk for birth defects include diabetes and obesity.

If you are pregnant or planning to get pregnant, see your healthcare provider. Prenatal (before birth) care can help find some problems early in pregnancy so that they can be monitored or treated before birth.

Birth defects are generally grouped into three major categories:

Structural/metabolic abnormalities:

  • Occur when some part of the body (internal or external) is missing, is not shaped or working properly or when the body is unable to metabolize certain substances due to an inborn genetic error.
  • Heart defects are the most common type of structural birth defect, affecting one baby in 125.
  • Examples of metabolic disorders include Tay-Sachs disease or Phenylketonuria (PKU).

Congenital infections:

  • The most common is Rubella or German measles.
  • Pregnant women infected with Rubella during their first trimester of pregnancy are at increased risk for having a baby born with one or more features of Congenital Rubella Syndrome (deafness, mental retardation, heart defects and blindness).
  • With widespread vaccination, this syndrome is now rare in the United States.

Other causes:

  • Environmental factors such as drug or alcohol abuse, and exposure to certain prescription medications or other chemicals.

Frequently Asked Questions

Does PA screen newborns for birth defects?

What are neural tube defects?
Neural tube defects (NTD) occur when the brain and spinal cord do not form properly. The neural tube is the embryonic structure that develops into the brain and spinal cord. This structure starts out as a small ribbon of tissue that normally folds inward to make a tube by the 28 th day after a woman becomes pregnant.

When this process does not work properly, the neural tube does not close completely and the brain and spinal cord may not develop normally. Approximately 2,500 babies are born in the United States each year with birth defects of the brain and spinal cord. In these cases where the brain and spinal cord do not develop properly, the pregnancy sometimes ends in a miscarriage or stillbirth.

What are common neural tube defects? 

  • Anencephaly – A fatal birth defect that happens when the neural tube does not fully close at the top. As a result, part of the skull and brain are missing. Babies with anencephaly die before or shortly after birth.
  • Spina Bifida - Often called "opened spine," the bony spinal column and soft tissue layer over the spine do not form properly, leaving the spinal cord exposed. Children with a severe case of spina bifida may have some bladder and bowel control problems and paralysis in their legs.
  • Encephalocele - A condition resulting in abnormal closure of the skull where a portion of the brain is contained in a sac outside the skull.

Can birth defects be prevented?
There are a number of steps a woman can take to reduce her risk of having a baby with a birth defect. An important first step is a pre-pregnancy visit with a health care provider to obtain information about risk factors for a birth defect or inherited genetic condition. Other steps include taking a multivitamin containing 400 micrograms of folic acid and avoiding alcohol, smoking and drugs during pregnancy.

What types of services does the Department of Health provide regarding birth defects prevention? 
The Department participates in National Birth Defects Prevention Month recognized each year in January. The goal of Birth Defects Prevention Month is to create awareness that birth defects are the leading cause of death in children less than one year old and that some birth defects are preventable.

What types of services does the Department of Health provide for parents of Children with Special Health Care Needs?
Special Kids Network (SKN), a statewide information and referral resource for families and caregivers of children with special needs and the providers who serve them. If you are the parent or caregiver of a child who has special needs, this free program can provide you with support, up-to-date information, and referrals to statewide agencies and organizations that serve children with special health care needs. Visit the SKN website or call the toll-free number at 1-800-986-4550.