Birth defect

Congenital anomalies per 100,000 inhabitants in 2004.

Charles II of Spain was born mentally and physically disabled, probably caused by inbreeding in the House of Habsburg

Congenital abnormalities present at birth

Birth defects are structural or functional abnormalities present at birth that can affect any part of the body, including organs, limbs, metabolism, and development. These defects can vary in severity, ranging from mild conditions that require little to no medical intervention to severe abnormalities that may cause disability or death. Birth defects can be genetic, environmental, or multifactorial in origin.

Epidemiology

Birth defects occur worldwide and are one of the leading causes of infant mortality and childhood disabilities. Some key epidemiological facts include:

• Affect approximately 1 in 33 newborns worldwide.
• Account for a significant percentage of infant deaths globally.
• Can be detected prenatally, at birth, or later in life, depending on severity and type.

Causes of Birth Defects

Birth defects arise from a combination of genetic, environmental, and unknown factors. The major causes include:

Genetic Factors

Genetic birth defects occur due to mutations in DNA or chromosomal abnormalities. These may be inherited or result from spontaneous mutations.

• Chromosomal disorders – Conditions such as Down syndrome (Trisomy 21), Turner syndrome, and Klinefelter syndrome.
• Single-gene mutations – Conditions such as cystic fibrosis, sickle cell anemia, and Tay-Sachs disease.

Environmental Factors

Certain environmental factors can interfere with fetal development and lead to birth defects:

• Teratogens – Substances that can cause birth defects, including:
• Alcohol – Causes fetal alcohol spectrum disorders (FASD).
• Drugs – Certain medications, including thalidomide, isotretinoin, and some anticonvulsants.
• Infections – Congenital infections such as rubella, cytomegalovirus (CMV), toxoplasmosis, and syphilis.
• Radiation – Exposure to high levels of radiation can lead to fetal malformations.
• Tobacco and pollutants – Can increase the risk of low birth weight and congenital abnormalities.

Multifactorial Causes

Many birth defects result from a combination of genetic and environmental factors. Conditions such as neural tube defects (spina bifida, anencephaly) and congenital heart defects fall into this category.

Types of Birth Defects

Birth defects can be categorized based on their impact on different body systems:

Structural Birth Defects

Structural defects involve physical abnormalities in the body's formation:

• Neural tube defects – Spina bifida, anencephaly, encephalocele.
• Congenital heart defects – Tetralogy of Fallot, atrial septal defect, ventricular septal defect.
• Cleft lip and cleft palate – Affects the mouth and facial structure.
• Limb deformities – Clubfoot, missing or extra fingers (polydactyly, syndactyly).
• Gastrointestinal defects – Hirschsprung's disease, gastroschisis, omphalocele.

Functional or Developmental Birth Defects

These defects impact organ function, metabolism, or brain development:

• Metabolic disorders – Phenylketonuria (PKU), galactosemia, maple syrup urine disease.
• Neurological disorders – Cerebral palsy, microcephaly, hydrocephalus.
• Sensory impairments – Congenital hearing loss, blindness.
• Endocrine disorders – Congenital hypothyroidism, adrenal hyperplasia.

Diagnosis

Birth defects can be diagnosed through prenatal screening, newborn screening, and physical examinations.

Prenatal Diagnosis

• Ultrasound imaging – Detects physical abnormalities in fetal development.
• Amniocentesis – Used to analyze genetic material for chromosomal disorders.
• Chorionic villus sampling (CVS) – Early genetic testing for chromosomal abnormalities.
• Maternal serum screening – Identifies markers for Down syndrome, trisomy 18, and neural tube defects.

Newborn Screening

Many countries conduct newborn screening for common metabolic and genetic conditions, such as:

• Phenylketonuria (PKU)
• Congenital hypothyroidism
• Cystic fibrosis
• Sickle cell disease

Postnatal Diagnosis

Some birth defects are not detected at birth and only become evident as the child grows. These include developmental delays, sensory impairments, and metabolic disorders.

Prevention

While not all birth defects are preventable, several strategies can reduce the risk:

Preconception and Prenatal Care

• Folic acid supplementation – Reduces the risk of neural tube defects.
• Avoidance of alcohol, smoking, and illicit drugs – Prevents fetal alcohol spectrum disorders and other defects.
• Vaccination against infections (e.g., rubella) – Prevents congenital infections.
• Managing chronic conditions (e.g., diabetes) – Helps control risks associated with pregnancy.
• Avoiding harmful medications during pregnancy – Consult with a healthcare provider before taking any drugs.

Genetic Counseling

For individuals with a family history of birth defects, genetic counseling can provide:

• Risk assessment for inherited conditions.
• Options for prenatal genetic testing.
• Reproductive planning strategies.

Treatment and Management

The management of birth defects depends on their type, severity, and impact on health. Some defects may require surgical correction, while others involve long-term medical care.

Surgical Interventions

Many structural birth defects can be corrected or improved with surgery:

• Congenital heart defects – May require open-heart surgery.
• Cleft lip and cleft palate – Corrected through reconstructive surgery.
• Neural tube defects – Spina bifida may require surgical closure.

Medical Management

Certain conditions require lifelong medical treatment:

• Metabolic disorders – Require dietary management (e.g., low-phenylalanine diet for PKU).
• Hormonal disorders – Congenital hypothyroidism treated with thyroid hormone replacement.
• Neurological disorders – Cerebral palsy may require physical therapy and assistive devices.

Supportive Therapy

Children with birth defects may benefit from:

• Physical therapy and occupational therapy.
• Speech and developmental therapy.
• Assistive devices (e.g., hearing aids, prosthetic limbs).

Prognosis

The long-term outlook for children with birth defects varies widely:

• Mild defects may cause no significant health problems.
• Severe defects can result in lifelong disabilities or early mortality.
• Early diagnosis and intervention can significantly improve quality of life.

Complications

Without proper management and treatment, birth defects can lead to:

• Physical disabilities.
• Intellectual disabilities.
• Increased risk of infections and chronic diseases.
• Emotional and psychological impact on families.

Conclusion

Birth defects are a major global health concern, but advancements in medicine, genetic research, and prenatal care have significantly improved outcomes for affected individuals. Early detection, prevention strategies, and appropriate medical intervention are essential in managing and reducing the impact of birth defects.

See Also

• Congenital disorder
• Genetic counseling
• Neonatology
• Prenatal care

External Links

• CDC – Birth Defects
• March of Dimes – Birth Defects

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