Home Types of Birth Defects: Causes, Categories & Prevention

Types of Birth Defects: Causes, Categories & Prevention

Birth defects, also called congenital malformations, are conditions present at birth that affect how the body looks, works, or both. In the U.S., a child is born with a major birth defect every 4 1/2 minutes, making these conditions a leading cause of infant mortality and lifelong disability.

Because many defects aren’t obvious at birth, follow-up studies show that half of major anomalies go undiagnosed until later in childhood—so the true incidence rises from about 3% at birth to at least 6% (and up to 16% by age 5 in some cohorts).

 

Families, healthcare providers, and the community as a whole need to be aware of the many different types of birth defects. The better we understand and identify these conditions, the more we can prevent them, detect them early, and ensure children get the care they need.

Birth Defects Types: Key Facts

  • In the U.S., a major birth defect occurs in about 1 in every 4.5 minutes, making them a leading cause of infant death and disability. While 3% are diagnosed at birth, follow-up studies reveal the true rate may reach 6–16% by age 5.
  • Main Types of Birth Defects

    • Structural: Physical malformations such as congenital heart defects, cleft lip/palate, spina bifida, and limb abnormalities.

    • Functional (Developmental): Conditions affecting how a body system works, like autism, intellectual disabilities, metabolic disorders, and sensory impairments.

  • Birth defects can affect nearly any system, including:

    • Neural tube defects (risk reduced ~70% with folic acid)

    • Congenital heart defects

    • Chromosomal disorders

    • Orofacial clefts

    • Limb/skeletal defects

    • GI malformations, genitourinary defects, and rare multi-system syndromes.

  • About 80% of birth defects stem from a gene–environment interaction, while only ~20% are due to genetics alone. Both maternal and paternal exposures can contribute.
  • Many birth defects can’t be fully prevented, but risks can be reduced with folic acid supplementation, avoiding alcohol/tobacco, managing chronic conditions, reviewing medications, and limiting toxic exposures. Early detection and intervention—through surgery, therapies, and ongoing medical care—can make a meaningful difference, but outcomes vary widely and many families face significant emotional and financial challenges.

 

 

At Birth Defect Research for Children (BDRC), we’re proud to be the only organization in the world collecting detailed data on both maternal and paternal birth defects—including both functional and structural types—through the National Birth Defect Registry.

Research shows that about 80% of birth defects result from an interaction between genetic predispositions and environmental triggers, while only around 20% are caused by genetics alone. This means that increasing awareness and reducing risk factors can make a real difference for families everywhere.

 

 

Types of Birth Defects: Structural vs. Functional

Birth defects can affect any part of the body and may range from mild to severe. Some are discovered before birth through prenatal screening, while others become apparent only as a child grows.

There are two main categories: structural birth defects and functional (developmental) birth defects.

Structural Birth Defects

Structural birth defects are problems with how parts of the body are formed. Common examples include congenital heart defects, cleft lip or palate, neural tube defects like spina bifida, and limb abnormalities. These are typically visible or can be detected through medical imaging.

In other words, they are caused by the improper formation of organs or body parts, often developing early in pregnancy, and may impact appearance, function, or both.

Functional (Developmental) Birth Defects

Functional or developmental birth defects are conditions that affect how a part of the body or a body system works, even when everything may appear normal on the outside. These can include metabolic disorders like phenylketonuria (PKU), neurodevelopmental conditions such as autism spectrum disorders or intellectual disabilities, and sensory deficits like hearing loss. Unlike many structural birth defects—which may be visible at birth—functional birth defects often become apparent only as a child grows and develops.

In other words, these are problems with the way a body part or system operates, which might not be immediately obvious but can show up as developmental delays, learning differences, behavioral challenges, or metabolic issues later in life. While many parents may not think of conditions like autism as birth defects, our research tells a more complex story. Data collected by Birth Defect Research for Children (BDRC) shows that roughly 60% of children diagnosed with autism also have a structural birth defect. This significant overlap suggests that both functional and structural conditions may stem from disruptions or exposures during early fetal development—highlighting how interconnected these processes truly are.

As science continues to explore the underlying causes of functional birth defects, BDRC is at the forefront of investigating environmental and genetic factors. Our next major project will address the possible connection between autism and prenatal exposure to acetaminophen (Tylenol®). Once our report is complete, we will share the findings here to help families and clinicians better understand the early influences that can shape a child’s lifelong health.

Learn more about the difference between functional and structural birth defects.

 

Major Categories of Birth Defects

Birth defects are often grouped by the organ system they affect. Each category below includes definitions, common examples, causes, symptoms, methods of diagnosis and screening, treatment approaches, and outlook for affected children and families.

Neural Tube Defects

Neural tube defects are malformations that affect the brain, spine, or spinal cord. These defects occur very early in pregnancy, often before a woman knows she is pregnant. Examples include spina bifida, where part of the spinal cord does not develop properly; anencephaly, a severe condition where parts of the brain and skull are missing; and encephalocele, in which brain tissue protrudes outside the skull.

How does folic acid help?

Research has shown that taking folic acid before conception and during early pregnancy can reduce the risk of neural tube defects by about seventy percent. Neural tube defects may be caused by a combination of folate deficiency, certain variants, and specific medications.

Symptoms can vary but often include mobility problems, learning difficulties, and fluid on the brain (hydrocephalus). These conditions are often detected through prenatal ultrasound and blood tests. Treatment may involve surgery (sometimes before birth), physical therapy, and ongoing medical management. The long-term outlook depends on the type and severity of the defect, but early intervention can greatly improve quality of life.

Congenital Heart Defects

Congenital heart defects are problems with the structure of the heart or blood vessels that are present at birth. These can range from simple conditions that cause few symptoms to complex malformations that are life-threatening. Examples include Tetralogy of Fallot, ventricular septal defect (a hole in the wall separating the lower heart chambers), and persistent truncus arteriosus.

Children with heart defects may experience symptoms such as bluish skin color (cyanosis), rapid breathing, and poor feeding. Diagnosis often occurs before birth with fetal echocardiogram or shortly after birth using pulse oximetry. Treatments include medications, surgery, or catheter-based interventions. Many children with congenital heart defects can live full, healthy lives with appropriate care.

Chromosomal Disorders

Chromosomal disorders are caused by changes in a child’s chromosomes—either extra, missing, or rearranged genetic material. Common examples are Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and Patau syndrome (Trisomy 13).

How do genetics contribute?

These conditions are most often caused by errors in cell division, either inherited from parents or occurring spontaneously. Symptoms can include distinctive facial features, developmental delays, intellectual disability, and heart defects, depending on the specific syndrome. Diagnosis is usually made through prenatal screening tests such as noninvasive prenatal testing (NIPT) and confirmed by genetic testing like amniocentesis or karyotyping. Early intervention programs and supportive therapies can improve health outcomes and developmental progress.

More information on Chromosomal Disorders

Orofacial Clefts

Orofacial clefts are openings or splits in the lip and/or roof of the mouth (palate) that develop during pregnancy. Cleft lip and cleft palate are the most common examples. These conditions can be caused by a mix of genetic and environmental factors, including maternal smoking, diabetes, and some medications.

Children born with orofacial clefts may have difficulties with feeding, speech, and frequent ear infections. Most cases are diagnosed during a prenatal ultrasound or at birth. Treatment often involves a series of surgeries, as well as ongoing speech therapy and dental care. While many children do well with comprehensive, team-based care, some families may face multiple surgeries, speech and dental challenges, and ongoing emotional or financial burdens. Outcomes can vary, and ongoing support is important for both children and their families.

Limb Reduction & Skeletal Defects

Limb reduction and skeletal defects refer to missing or underdeveloped bones or limbs, and disorders of bone development. Clubfoot, where the foot is twisted out of shape or position; limb absence or reduction, in which part of a limb fails to form; and craniosynostosis, where the bones in a baby’s skull fuse too early, are some key examples.

Children with limb reduction or skeletal defects may show visible differences or difficulties in movement and coordination. Diagnosis is often made by ultrasound before birth or by X-ray after birth. Treatment can include surgical correction, orthotic devices, and physical therapy. While some children adapt well and achieve greater independence with the right support, many may face long-term mobility challenges and ongoing emotional or financial burdens. Outcomes vary widely, and continued access to care and support is important for both children and their families.

Other examples of skeletal defects

Digestive / GI Malformations

Digestive and gastrointestinal malformations include conditions such as gastroschisis (where the intestines are outside of the baby’s body), omphalocele (abdominal organs protrude into the base of the umbilical cord), and Hirschsprung disease (missing nerve cells in the colon).

Symptoms can include feeding problems, vomiting, and abdominal swelling. Most are diagnosed by prenatal imaging or soon after birth. Treatment involves surgical repair and, for some, ongoing nutritional and medical support.

Genitourinary Defects

Genitourinary defects are abnormalities in the urinary or genital systems. Examples include hypospadias (where the opening of the urethra is not at the tip of the penis), undescended testicles, and imperforate anus (no opening at the end of the digestive tract).

What prenatal tests detect these?

Many of these conditions are identified through routine prenatal ultrasound and confirmed after birth with a physical examination. Surgical correction is often required, and while early intervention and appropriate care can significantly improve outcomes, results can vary depending on the severity of the condition, the success of surgical procedures, and the need for ongoing management. Some children may experience lasting challenges and require continued support as they grow.

Rare & Complex Syndromes

Rare and complex birth defect syndromes, such as VACTERL association, CHARGE syndrome, amniotic band syndrome, and Dandy-Walker malformation, involve multiple organ systems and require coordinated, multidisciplinary care. Symptoms are diverse and may affect bones, organs and overall development. Diagnosis often requires genetic testing and specialist evaluation.

Explore more birth defect statistics and trends on our data and research page.

 

Causes and Risk Factors

Birth defects often result from a combination of genetic and environmental influences. Some are linked to inherited genes, chromosomal changes, or spontaneous mutations that occur during fetal development. However, a large portion are related to external factors that can affect either parent before or during pregnancy.

The risk of birth defects is higher with substance use in pregnancy, some infections, exposure to specific medications, poorly managed maternal health conditions, and advanced maternal age. Often, birth defects result from the interaction between genetic susceptibility and environmental exposure.

Common causes of birth defects

  • Genetic factors:
    • Inherited gene changes (dominant or recessive)
    • New (de novo) mutations arising during fetal development
    • Chromosomal errors (extra, missing, or rearranged material)
  • Environmental factors (teratogens):
    • Alcohol and tobacco use during pregnancy
    • Over-the-counter and prescription medications
    • Household chemicals (pesticides, cleaning products)
    • Workplace exposures
    • Certain infections (rubella, Zika)
    • Poorly managed maternal health conditions (diabetes, obesity)
    • Advanced parental age

Genetic causes include inherited gene changes, new mutations, and chromosomal errors that can disrupt normal development. Environmental causes—also known as teratogens—are much broader than many people realize. These include not only alcohol and illegal drugs, but also over-the-counter and prescription medications, exposure to household and workplace chemicals (such as pesticides, certain cleaning products, or salon products), as well as viral infections like rubella or Zika. Uncontrolled diabetes, poorly managed maternal health conditions, and advanced parental age also increase risk. It’s important to recognize that both maternal and paternal exposures can contribute to birth defects, and in some cases, risks can even be passed from the father to the developing baby.

Birth Defects in Children of Military Personnel

Some of the most significant research on environmental causes of birth defects comes from studies of military personnel and their families. Birth Defect Research for Children (BDRC) has been studying birth defects among the families of Vietnam veterans since 1986, working with the University of South Carolina and the New Jersey Agent Orange Commission to counsel families, produce fact sheets and launch the National Birth Defect Registry to document the disabilities they were reporting. Thousands of case reports from Vietnam veterans have revealed a consistent pattern of structural and functional birth defects in their children, often linked to toxic exposures such as dioxin‑contaminated herbicides.

When Gulf War veterans began returning, BDRC’s scientific advisory board established a special section of the registry to track birth defects in these veterans’ children and pushed for national studies of intergenerational effects of war service. The organization’s advocacy contributed to the passage of a Toxic Exposure Research bill that authorizes research into the health of descendants of veterans exposed to military toxins. This work highlights how environmental exposures—including those experienced during military service—can impact not just one generation but also the children of exposed individuals.

Prevention and Risk Reduction

While not all birth defects can be prevented, the risk can be greatly reduced by making healthy choices and taking preventive steps.

Folic Acid supplementation

Taking 400 micrograms of folic acid every day, before conception and during early pregnancy, has been shown to reduce the risk of neural tube defects by about seventy percent. Women of childbearing age are encouraged to take folic acid supplements and eat foods rich in folate.

Maintaining a healthy lifestyle before and during pregnancy is vital for reducing the risk of birth defects. It is important to avoid alcohol and tobacco, manage chronic conditions like diabetes or obesity, and follow a balanced diet. One of the most crucial steps is to review all prescription and over-the-counter medications with a healthcare provider before trying to conceive or during pregnancy, since some medications and supplements can increase the risk of birth defects.

In addition, parents should be mindful of toxic exposures at home—such as pesticides and household cleaning products—as well as at work, including settings like nail salons or industrial environments. Avoiding unnecessary chemical exposures and seeking guidance on medication safety are key parts of preconception care and pregnancy planning.

For practical tips on lowering risks and supporting a healthy pregnancy, visit our Healthy Baby Resource.

Screening & Diagnosis

Several tests are available to screen for and diagnose birth defects. Prenatal ultrasound can detect many structural issues. Blood tests, including cell-free DNA testing, can screen for chromosomal abnormalities. More definitive genetic diagnoses are made through procedures like amniocentesis and chorionic villus sampling.

At birth, a thorough newborn examination can detect many physical and some metabolic conditions. As children grow, developmental screening helps identify issues with learning, speech, or behavior.

Management and Outlook

Early detection and intervention can make a significant difference in outcomes for children with birth defects. Medical treatments may include surgery—such as repair of a cleft palate or heart defect—or therapies like physical, occupational, and speech therapy. Ongoing medical care may be necessary for associated conditions.

Families are encouraged to access early intervention services and connect with support groups and specialized programs for their child’s condition. While early intervention and comprehensive support can make a meaningful difference, outcomes for children with birth defects vary widely. Many families face significant emotional, financial, and social challenges, and it’s important to recognize the ongoing support that parents and caregivers may need throughout their child’s life.

 

How We Can Help

If you’re a community group or local health agency concerned about a cluster of birth defects, visit our Community Resource page to request an environmental investigation. Families seeking peer support and guidance can find help on our Parent Support Pages, which include links to support groups and our parent-matching program.

Parents should also seek a comprehensive medical evaluation and build a care team of specialists, therapists, and community organizations.

BDRC is a recognized leader in the field, with a long history of supporting families and advancing public health. We’ve successfully advocated for the removal of harmful drugs from the market, uncovered environmental causes behind cleft-palate clusters, verified the causes of gastroschisis, and pioneered research into male-mediated birth defects—studying how paternal exposures and pre-conception factors contribute to anomalies.

Our National Birth Defect Registry is unique in collecting detailed data on both maternal and paternal risk factors, with special emphasis on over-the-counter medications, household toxins like pesticides and cleaning products, and workplace exposures, including nail-salon chemicals.

Research shows about 80% of birth defects involve gene–environment interactions, not genetics alone. While early intervention and support can help, outcomes vary widely and many families face significant emotional and financial challenges. BDRC remains committed to guiding families, fostering a supportive community, and advancing research to improve prevention and awareness.

 

Frequently Asked Questions

 

 

Can birth defects be prevented entirely?

While not all birth defects are preventable, adopting healthy behaviors and following medical guidance can reduce the risk for many conditions.

Is prenatal diagnosis always accurate?

Prenatal screening and diagnostic tests are highly reliable but not perfect. Some conditions may not be detected until after birth or as a child grows.

What should parents do if a birth defect is detected?

For neighborhood or municipal inquiries (like investigating a potential toxin spill), start at the Community Resource page. If you’re a parent looking for emotional support or to connect with other families, head over to the Parent Support Pages.

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