Congenital Anomalies

Congenital anomalies are structural or functional anomalies present at birth that can cause physical disability, intellectual and developmental disabilities (IDDs), and other health problems.^1,2 Some may be fatal, especially if not detected and treated early.

There are two main categories of congenital anomalies: structural and functional/developmental. This information focuses on structural congenital anomalies, their causes, their prevention, and their treatment. Functional/developmental congenital anomalies are addressed more completely in the IDDs content.

Some congenital anomalies affect many parts or processes in the body, leading to both structural and functional problems.

Researchers have identified thousands of different congenital anomalies. According to the Centers for Disease Control and Prevention (CDC), congenital anomalies are the leading cause of death for infants in the United States during the first year of life.³

There are two main categories of congenital anomalies.

Structural Congenital Anomalies

Structural congenital anomalies are related to a problem with the structure of body parts. These can include:

• Cleft lip or cleft palate
• Heart defects, such as missing or misshaped valves
• Atypical limbs, such as a clubfoot
• Neural tube defects, such as spina bifida, and problems related to the growth and development of the brain and spinal cord

Functional or Developmental Congenital Anomalies

Functional or developmental congenital anomalies are related to a problem with how a body part or body system works or functions. These problems can include:

• Nervous system or brain problems. These include intellectual and developmental disabilities, behavioral disorders, speech or language difficulties, seizures, and movement trouble. Some examples of congenital anomalies that affect the nervous system include Down syndrome, Prader-Willi syndrome, and Fragile X syndrome.
• Sensory problems. Examples include hearing loss and visual problems, such as blindness or deafness.
• Metabolic disorders. These involve problems with certain chemical reactions in the body, such as conditions that limit the body’s ability to rid itself of waste materials or harmful chemicals. Two common metabolic disorders are phenylketonuria and hypothyroidism.
• Degenerative disorders. These are conditions that might not be obvious at birth but cause one or more aspects of health to steadily get worse. Examples of degenerative disorders are muscular dystrophy and X-linked adrenoleukodystrophy, which leads to problems of the nervous system and the adrenal glands and was the subject of the movie "Lorenzo’s Oil."

Some congenital anomalies affect many parts or processes in the body, leading to both structural and functional problems.

This information focuses on structural congenital anomalies, their causes, their prevention, and their treatment. Functional/developmental congenital anomalies are addressed more completely in the intellectual and developmental disabilities content.

CDC estimates that congenital anomalies occur in about 1 in every 33 infants born in the United States each year.¹

Congenital anomalies can occur during any pregnancy, but some factors increase the risk. The following situations place pregnant people at higher risk of having a child with a congenital anomaly:²

• Lack of folic acid. People who are pregnant or who could become pregnant should take 400 micrograms of folic acid every day to prevent neural tube defects (NTDs). However, according to the Centers for Disease Control and Prevention (CDC), only 2 out of every 5 people of childbearing age take folic acid every day.³
• Drinking alcohol. Drinking alcohol during pregnancy can lead to a variety of problems, including congenital anomalies. For example, using alcohol can lead to a fetal alcohol spectrum disorder, which is characterized by intellectual or developmental disabilities (IDD), physical challenges, and behavioral problems. There is no safe level of alcohol consumption during pregnancy.⁴
• Smoking cigarettes. Smoking cigarettes during pregnancy can lead to a variety of problems, including lung problems such as asthma. Evidence also strongly suggests that certain congenital anomalies, such as cleft lip or cleft palate, are caused by smoking during pregnancy.⁵
• Using drugs. Using drugs during pregnancy can increase the risk of various congenital anomalies, including IDDs and behavioral problems, as well as pregnancy loss and stillbirth.⁶
• Medication use. Certain medications are known to cause congenital anomalies if taken during pregnancy. Thalidomide, which is currently used to treat certain cancers and other serious conditions, was once sold as a treatment for morning sickness until it was discovered that it caused severe congenital anomalies. Infants whose mothers took thalidomide had a range of structural and functional problems, including misshapen ears and shortened limbs. Although the thalidomide situation led to much stricter controls on drugs used during pregnancy, most medications currently used by pregnant people have not been tested for safety or efficacy in pregnant people. Addressing this issue is the primary focus of Maternal and Pediatric Precision in Therapeutics (MPRINT) Hub . People who are pregnant or who might become pregnant should discuss all medications, both prescription and over-the-counter, and supplements they take with their health care providers.⁷
• Infections. People who get certain infections during pregnancy are at higher risk for having a child with congenital anomalies. Some of the more common infections linked to congenital anomalies are cytomegalovirus, a common virus that spreads through body fluids and usually causes no symptoms in healthy people, and toxoplasmosis, a parasitic infection that spreads through contact with cat feces, raw meat, and contaminated food and water. Zika virus infection is linked to microcephaly in newborn babies—a condition in which the brain and skull are atypically small. The Pregnancy topic has more information on infections that can cause congenital anomalies and other problems in newborns and on ways to prevent them during pregnancy, and CDC provides tips for preventing infections before and during pregnancy.
• Obesity or uncontrolled diabetes. NICHD research found that the risk of newborn heart defects and NTDs increased with maternal obesity. Additional NICHD research suggest that children of parents with obesity may be at risk for developmental delays. Obesity is also associated with health problems and long-term health issues. Poorly controlled blood sugar places women at higher risk of having a baby who is too large, has breathing problems, or has other poor health outcomes. These outcomes are likely regardless of whether the woman had diabetes before she got pregnant (type 1 or 2 diabetes) or whether she developed diabetes during pregnancy (gestational diabetes).⁸
• Exposure to things in the environment. Pregnant people who breathe in, eat, drink, or get things into their bodies in other ways may also be at increased risk of congenital anomalies. For example, pregnant people who are exposed to high levels of radiation, such as cancer treatments, are at higher risk for congenital anomalies in their infants.⁹ Handling or breathing in certain chemicals can also increase the risk of congenital anomalies.¹⁰

Different congenital anomalies have different causes, and the causes of many congenital anomalies remain unknown.

A specific condition might be caused by one or more of the following primary problems:¹

• Genetic problems. One or more genes might have a change or mutation that results in them not working properly, such as in Fragile X syndrome. Similarly, a gene or part of the gene might be missing.
• Chromosomal problems. In some cases, a chromosome or part of a chromosome might be missing, such as in Turner syndrome, when a female is missing an X chromosome. Other congenital anomalies result from having an extra chromosome, such as in Klinefelter syndrome and Down syndrome.
• Infections. Women who get certain infections during pregnancy are at higher risk for having a child with birth defects. For example, infection with Zika virus during pregnancy is linked with the congenital anomaly called microcephaly, in which the brain and skull are atypically small. Zika infection in pregnancy is linked to other structural problems with the brain as well. Our Pregnancy topic has more information on infections that can cause congenital anomalies and other problems in newborns and on ways to prevent them during pregnancy, and CDC provides tips for preventing infections before and during pregnancy.
• Exposure to medications, chemicals, or other agents during pregnancy. The infants whose mothers took thalidomide are examples of an exposure leading to congenital anomalies. Other examples include exposure to rubella (also called German measles) and toxic chemicals, such as hydrocarbons.²

Diagnosis of congenital anomalies depends on the specific problem and parts or systems of the body that are affected.

Many structural problems, such as club foot or cleft palate, are detected and diagnosed after a physical examination of the baby immediately after birth. For other conditions, newborn screening or prenatal testing is the only way to detect and diagnose problems.

This information focuses on structural congenital anomalies, their causes, their prevention, and their treatments. Functional/developmental congenital anomalies are addressed more completely in the intellectual and developmental disabilities content and in condition-specific topics.

Newborn Screening

Newborn screening, a process that tests infants' blood for different health conditions, including many congenital anomalies, provides one method of detecting problems. Newborn screening does not diagnose any specific conditions but detects that a problem may exist. By detecting problems immediately after birth, conditions can be diagnosed and treated before they have lifelong effects.

In addition, newborn screening routinely includes test for hearing problems, as well as pulse oximetry (test of baby's pulse rate and blood oxygen levels) to detect critical congenital heart defects.¹

Infants who are at high risk for certain conditions—for example, because of their family history—can undergo additional testing at birth to detect these conditions and treat them if needed. This type of screening has been effective in detecting some cases of Menkes disease, allowing for treatment to begin before health problems occur.

Prenatal Screening

During pregnancy, pregnant people have routine tests, such as blood and urine tests, to check for diabetes, signs of infection, or disorders of pregnancy such as preeclampsia. Blood tests also measure the levels of certain substances in a pregnant person’s blood that determine the risk of the fetus for certain chromosomal disorders and neural tube defects. Ultrasound screenings, creating a picture using sound, allow providers to view the developing fetus in the womb. Some congenital anomalies, such as spina bifida, are detectable on ultrasounds.

Health care providers recommend that certain pregnant people, including those who are older than 35 years of age and those with a family history of certain conditions, get additional prenatal tests to screen for congenital anomalies. Prenatal detection allows doctors to start treatment as early as possible for some congenital anomalies.

Noninvasive prenatal testing (NIPT)^2,3

NIPT is not a routine prenatal test but is used when a routine test suggests that the fetus may have a chromosomal disorder, such as having an extra or missing chromosome in each cell, which occurs in disorders such as Down syndrome, Patau syndrome, and Edwards syndrome.

NIPT analyzes the placental DNA present in the mother's blood; it does not require cell samples from inside the womb.

Currently, experts recommend NIPT only for high-risk pregnancies.⁴ This method does not detect open neural tube defects, nor does it predict late pregnancy complications.

Amniocentesis⁵

Amniocentesis is a test that is usually performed to determine whether a fetus has a genetic disorder. In this test, a health care provider takes a small amount of fluid from the womb using a long needle. The fluid, called amniotic fluid, contains cells that have genetic material that is the same as the fetus's genetic material. A laboratory grows the cells and then examines their genetic material for any problems. Some congenital anomalies that can be detected with amniocentesis are Down syndrome and certain types of muscular dystrophy.

There is a slight risk of pregnancy loss with amniocentesis, so pregnant people should discuss the procedure with their health care provider before making a decision about the test.

Chorionic Villus Sampling (CVS)^6,7

This test extracts cells from inside the womb to determine whether the fetus has a genetic disorder. Using a long needle, the health care provider takes cells from the chorionic villi, which are tissues in the placenta, the organ in the womb that nourishes the fetus. The genetic material in the chorionic villus cells is identical to that of the fetal cells.

Like amniocentesis, CVS can be used to test for chromosomal disorders and other genetic problems. CVS can be done earlier in pregnancy than amniocentesis, but it is also associated with a slightly higher risk of miscarriage than amniocentesis. Pregnant people who are considering CVS should discuss the test and the risks with their health care provider.

Links to more information about prenatal testing are available in the Resources section of this topic.

Because the symptoms and problems caused by congenital anomalies vary, treatments also vary. Treatments range from medications and therapies to surgeries and assistive devices.

This information focuses on structural congenital anomalies, their causes, their prevention, and their treatments. Functional/developmental congenital anomalies are addressed more completely in the intellectual and developmental disabilities content and in the condition-specific topics.

For example:

• Steroid medications, such as prednisone, can help people with muscular dystrophy increase muscle strength, ability, and respiratory function and slow the progression of weakness. Physical therapy is also useful for building strength and reducing weakness.
• Infants with cerebral palsy may receive sensory-motor therapy using Velcro-covered "sticky mittens" to help them “snag” and explore objects they are unable to grasp in the hand.¹
• Assistive devices include orthopedic braces to help patients with limb anomalies to walk and cochlear implants for hearing impairment.
• In the Management of Myelomeningocele Study (MOMS), conducted through NICHD’s Maternal-Fetal Surgery Network, researchers tested a surgical procedure to correct a severe form of spina bifida while the fetus was still in the womb. Although the surgery itself carried risks, it greatly reduced health complications for the infants who received it, including greater likelihood of being able to walk without assistance. Visit https://www.nichd.nih.gov/newsroom/resources/spotlight/021011-spina-bifida-MOMS for more information.
• Gene therapy approaches, in which a gene that is mutated or missing is replaced by a typical version of the gene, are being tested for a variety of genetic disorders. Some examples of disorders that are being treated successfully with gene therapy include genetic disorders of the immune system, the muscles, and the eyes. Recent NICHD-supported research on Duchenne muscular dystrophy used genome editing techniques to improve leg grip strength in a mouse model by “turning on” a gene for a specific protein used in muscles.²

Visit https://clinicaltrials.gov/search?term=ongoing%20trials%20of%20gene%20therapies%20for%20genetic%20disorders to search for ongoing trials of gene therapies and other treatments for different congenital anomalies and genetic disorders.

If someone in your family has a congenital anomaly, find support and information through these resources, and discuss treatment options with that individual’s health care providers.