A birth defect, or congenital anomaly, is any medical condition a person has from birth. Congenital means acquired in the womb.

These medical conditions range from mild to more severe. Some affect the organs or a single body part, while others can affect development, how the body works, or the senses.

Most congenital anomalies have no obvious cause. Some are genetic, while others have a link to the woman’s health during pregnancy. It is also possible that environmental factors play a role.

Congenital anomalies affect around 3% of pregnancies. It is possible to reduce the chance of some of these irregularities, but not all of them.

In this article, learn more about congenital anomalies, including types, causes, and diagnosis.

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Most congenital anomalies have no obvious cause.

Congenital anomalies can be structural or developmental.

If they are structural, it means that they relate to body parts. If they are developmental, it means that they affect the way the body works, how a person learns, or the senses.

Some congenital anomalies have both structural and developmental effects. Examples of these include fragile X syndrome, spina bifida, and Down syndrome.

Structural anomalies

Some common structural congenital anomalies include heart defects, spina bifida, a cleft lip or palate, and clubfoot.

The sections below will outline some of these, plus some other, structural anomalies in more detail.

Heart defects

The most common congenital anomalies are heart defects. Most have no obvious cause, but if a pregnant woman has diabetes or smokes during pregnancy, it may increase the chance.

A heart anomaly occurs when part of the heart does not form properly in the womb. This can affect how well it can circulate blood around the body.

There are many different types of heart defect, depending on the affected area of the heart.

The most common heart defect is a ventricular septal defect. This is a hole in the wall separating the two lower heart chambers. Sometimes, the hole will close on its own over time.

Infants with severe heart defects often need surgery soon after birth.

Limb reduction

Sometimes, part of a limb will not fully form in the womb. Known as limb reduction, this structural anomaly means that a limb is smaller than the usual size or missing altogether. For example, an infant may have a missing finger, clubfoot, or an arm that is shorter than usual.

People with a minor limb reduction may find that it does not affect daily life. However, others may find certain movements limited, more difficult, or not possible. Physical therapy, splints, or prosthetics can help.

The cause of limb reduction is unknown. Exposure to chemicals or infections during pregnancy might increase the chance.

Cleft lip or palate

If the tissues forming the roof of the mouth or lip do not join properly, it can cause a cleft lip or palate. Some infants may have both.

This can affect speech, hearing, and eating. Most infants with this structural anomaly will need surgery in the first few months of life. In severe cases, they may need ongoing surgeries.

Neural tube defects

Neural tube defects affect the brain and spinal cord. These structural anomalies occur in the first few months of pregnancy, when the brain and spinal cord of a fetus are forming.

Types of neural tube defect include:

  • Anencephaly: This occurs when parts of the brain and skull do not form at all.
  • Encephalocele: This occurs when the neural tube does not close fully. The brain projects through an opening in the skull.
  • Spina bifida: This occurs when the spine does not form and close properly. This affects the nerves and spinal cord.

Both anencephaly and encephalocele are very rare. Spina bifida is more common, affecting 1 in every 2,758 births in the United States.

The symptoms of spina bifida can be mild or severe, depending on the part of the spine it affects. It can cause paralysis, learning difficulties, and bladder and bowel problems.

Taking folic acid during pregnancy can help prevent neural tube defects in the infant.

Gut and stomach anomalies

Sometimes, the stomach muscles do not form properly and leave a hole near the belly button. This can mean that the intestines or organs are outside of the body.

In gastroschisis, the abdominal wall does not completely close, so the bowel can push through and develop outside of the body. The organs will not have a protective sac. In omphalocele, which is associated with other anomalies, there is a protective sac around the organs.

In either case, an infant will need surgery soon after birth.

The muscle separating the chest and abdomen is called the diaphragm. If a hole forms in the diaphragm, the organs can begin to move into the chest. This is known as a diaphragmatic hernia.

An infant will need surgery and help to breathe until the lungs work normally.

Developmental issues

Developmental issues are not always congenital anomalies.

This list gives a brief overview of the types of congenital anomaly that cause developmental issues:

  • Down syndrome: A person with Down syndrome is born with an extra chromosome. This affects brain and body development. Around 1 in every 700 babies born in the U.S. have Down syndrome.
  • Visual impairments: A visual impairment affects sight. The cause is an irregular eye shape or the fact that the brain and eyes do not work together properly.
  • Hearing impairments: These occur when the ear does not work properly. Most infants will have a hearing screening before they are 1 month old. They may have some ability to hear, or they may be deaf. This can be genetic.
  • Fetal alcohol spectrum disorders: These can occur if a woman drinks alcohol during pregnancy. They can affect learning, growth, and development.
  • Cerebral palsy: This is the most common childhood motor disability. It affects balance, movement, and posture. It can occur if there is damage to the brain while it is developing.
  • Muscular dystrophy: This affects the muscles, which become weaker over time. There are different types of muscular dystrophy, depending on the group of muscles they affect.
  • Genetic disorders: Some genetic disorders can affect development. The most common example is fragile X syndrome. This affects normal brain development and can affect learning and behavior.
  • Specific language impairment: This is a communication disorder. It can affect a person’s ability to read, write, and speak.

It is not possible to prevent every congenital anomaly. Approximately 50% have no obvious cause, while some have a link to maternal health.

Maintaining good health and limiting risk factors can reduce the chance of health problems for the infant.

The Centers for Disease Control and Prevention (CDC) recommend taking the following steps to reduce the chance of congenital anomalies:

  • Take 400 micrograms of folic acid per day during pregnancy.
  • See a medical professional regularly.
  • Avoid alcohol, cigarettes, and recreational drugs.
  • Check that medications are safe to use in pregnancy.
  • Try to prevent infections.
  • Try to avoid getting too hot.
  • Seek prompt treatment for fever.
  • Maintain a moderate weight.
  • Manage diabetes as best as possible.

A lack of folic acid increases the chance of some medical conditions relating to the brain and spine. If these body parts do not develop properly in the womb, it can cause spina bifida.

Drinking alcohol during pregnancy increases the chance of fetal alcohol syndrome. This can cause brain damage and problems with growth and development.

Smoking during pregnancy increases the chance of cleft lip and palate. It can also increase the chance of premature birth and low birth weight.

Fever and exposure to high temperatures during pregnancy can increase the chance of certain congenital anomalies, especially those that involve the development of the brain and spinal cord.

Infections during pregnancy can increase the chance of hearing loss in the infant.

A medical professional can diagnose some congenital anomalies during pregnancy. Prenatal tests check the health of a pregnant woman and the developing fetus.

These tests include:

  • noninvasive prenatal screening
  • a nuchal translucency ultrasound scan
  • the quad screen

A screening test shows either a normal or an abnormal result. The latter may indicate a problem. However, a test may give an abnormal result even if nothing is wrong.

If a screening test reveals a potential problem, diagnostic tests can offer more information. For example, a high resolution ultrasound can look in more detail at the fetus. A cleft lip, limb anomalies, and heart defects may all show up on an ultrasound.

A doctor may also test a small piece of placenta or amniotic fluid. This test looks for genetic or chromosome disorders, such as Down syndrome.

Newborn screenings check an infant’s health immediately after birth. Some congenital anomalies may only be apparent at this stage. Other medical conditions, such as a heart defect, may only appear much later in life.

Genetic counseling is an option for prospective parents and caregivers who have concerns about congenital anomalies.

A genetic counselor will collect information on their personal and family history and use this to predict the likelihood of a genetic condition. They can then offer advice, support, and medical treatment.

Some minor congenital anomalies do not need treatment.

However, severe structural anomalies often need surgery shortly after birth. Prenatal testing can often detect a structural anomaly in the womb and help medical professionals, parents, and caregivers prepare.

Congenital anomalies can cause lifelong disability. A person may need additional care or support to live the fullest possible life. This can involve ongoing surgeries or long-term medication.

People can ask a doctor for advice, support, and information.

There are many types of congenital anomaly. The outlook will depend on the specific condition, how severe it is, and whether or not the infant receives prompt care after birth.

Severe congenital anomalies are the leading cause of infant death in the U.S.

Annually, structural anomalies affect around 3% of all babies born in the U.S. Developmental issues are more common, affecting around 17% of all babies born in the U.S. each year.

People with one or more of these conditions may need additional support or ongoing treatment. This can help them live as fully and as independently as possible.

Advice and support from medical professionals, as well as other families, can be an important resource.