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About Birth Defect

A birth defect is any abnormality present at birth that results in physical or mental disability or death. The abnormality may affect the child’s structure, ability to function or metabolism. According to the Centers for Disease Control and Prevention  (CDC), about 3 percent of infants born in the United States (about one in every 33 births each year) have some kind of birth defect. Furthermore, birth defects are the leading cause of death in the first year of life.


According to the American Academy of Family Physicians (AAFP), there are more than 4,000 different birth defects. They vary widely, from structural defects (e.g., heart defects, neural tube defects) to metabolic problems (e.g., phenylketonuria) and combinations of both. Many birth defects are genetic disorders caused by alterations to genes or chromosomes that affect normal development (e.g., Down syndrome, sickle cell anemia)

Some birth defects are caused by a single, well-documented factor, such as a missing or abnormal gene or chromosome. Many are caused by a combination of several factors, such as maternal age, smoking, or medication use. Substances or infections that affect a pregnant woman may also affect the developing fetus and cause birth defects.

Many birth defects are defined by their cause, including fetal alcohol syndrome (due to maternal alcohol consumption) and congenital rubella syndrome (due to an infection with rubella in the first trimester). However, the causes of most birth defects are not known.

Birth defects are often detected before birth. Defects that have not been prenatally detected and are not obvious when the infant is born are usually discovered through newborn screening tests. While most birth defects are discovered in infancy, within the first year of life, some others may not be detected until childhood or even adulthood.

Some birth defects require little treatment. Other defects cannot be treated or will result in early death regardless of treatment attempts. However, most birth defects lie somewhere between these two extremes and are treatable to some degree.

Many birth defects are corrected through surgery in early infancy. Others can be treated through nonsurgical means. Birth defects that cause mental retardation and other developmental disabilities can present lifelong challenges to both parents and children. A few birth defects can be treated before birth using injections or even prenatal surgery.

Not all birth defects can be prevented. However, there are steps a woman can take to reduce her risk of having a child with a birth defect. For example, taking 400 micrograms of folic acid (a type of B vitamin) daily has been shown to reduce the risk of neural tube defects when taken both before and during pregnancy. It is also important to control certain conditions such as diabetes and obesity before pregnancy. Pregnant women need to avoid smoking (including second-hand smoke), alcohol and recreational drugs. Women who are pregnant should also discuss all medications (including over-the-counter medications) and immunizations with a physician.

Types and differences of birth defects

According to the American Academy of Family Physicians (AAFP), there are more than 4,000 different birth defects, which can be classified in numerous ways. They vary widely, from structural defects (e.g., heart defects) to functional problems (e.g., blindness, deafness) to metabolic problems, where the body lacks or cannot process certain enzymes. Some birth defects may encompass one or more problems.

Birth defects may also be classified by their suspected cause, which may also vary. For example, many birth defects are genetic disorders that occur due to a problem present in the infant’s genetic structure and may also include structural, functional or metabolic disorders or any combination of the three.

Some of the most common birth defects include:

  • Heart defects. The most common structural birth defects. According to the March of Dimes, about one of every 100 to 200 infants is born with a heart defect. They can range in severity from mild to serious and may include holes in the heart or malformed heart chambers or valves. Many can be effectively treated using surgery or other means. Heart defects cause more infant deaths than any other birth defect.
  • Genital or urinary defects. According to the March of Dimes, around one in every 135 infants is born with a defect in his or her genital or urinary system. These birth defects range from mild to severe. One example is hypospadias, which may affect male infants. In infants with this defect, the urethral opening occurs on the underside of the penis instead of the tip. It can be corrected through surgery.
  • Cleft lip and/or palate (Orofacial clefts). According to the Centers for Disease Control and Prevention (CDC), around one in every 700 to 1,000 infants is born with an orofacial cleft. The disorder is more common among Asian, Hispanic and Native American infants. It can be repaired surgically.
  • Clubfoot. The incorrect formation of the bones, joints, muscles and blood vessels in the foot and ankle. It causes the feet to point down and turn in and usually limits the range of motion of the feet. According to the AAFP, clubfoot occurs in about one in every 735 infants in the United States each year. Treatment may involve casts and surgery.
  • Down syndrome. Among the most common genetic disorders. Down syndrome is caused by an extra chromosome and is characterized by slow growth, mental retardation and abnormal facial features. According to the CDC, Down syndrome occurs in around one in every 800 infants. It is more common in infants born to older mothers.
  • Congenital hip dislocation. Occurs when the round upper end of the thighbone fails to sit properly inside the socket of the pelvis. This can happen in one or both hips and tends to affect girls more than boys. It usually is detected at birth and is treated by placing the infant in a soft sling for six to nine months.
  • Congenital hypothyroidism. Occurs when an infant’s thyroid gland is absent or underdeveloped at birth. This prevents the child from producing enough thyroid hormone, a substance which supports normal growth and brain development. If not treated right away, this condition can lead to developmental delays and permanent retardation. To prevent this, infants are routinely given a blood test shortly after birth to check for congenital hyperthyroidism.
  • Cerebral palsy. A group of disorders that cause brain damage and affect muscle control. The degree of impairment varies greatly among patients. According to the AAFP, between two and six of every 1,000 infants in the United States (about 10,000 infants each year) are born with cerebral palsy. Mental retardation and other disabilities also occur in around 70 percent of patients with the condition, the AAFP reports.
  • Neural tube defects. Defects in the brain or spinal cord that occur in the first month of pregnancy. According to the CDC, they appear in around one in every 1,000 pregnancies. The most common neural tube defects include:
    • Spina bifida. The most common neural tube defect. This defect occurs when the vertebral column fails to close completely, leaving the spinal cord partially exposed. According to the March of Dimes, about one in every 2,000 infants is born with spina bifida. This defect can often be repaired surgically. Some children with spina bifida experience few problems, while others have some paralysis and other nerve problems.
    • Anencephaly. A neural tube defect that occurs when parts of the brain fail to develop. Infants born with this condition die at birth or shortly after. According to the AAFP, it affects about three in every 10,000 infants.
  • Sickle cell anemia. A genetic blood disorder characterized by an abnormal shape of the red blood cells. The condition typically results in chronic anemia, painful attacks and other health problems. According to the AAFP, about one in every 500 African American infants and around one in every 1,000 to 1,400 Hispanic infants are born with this condition.
  • Cystic fibrosis. A condition most common in Caucasians. Results in thick mucus in the lungs and other organs, causing breathing and other problems. The American Academy of Pediatrics (AAP) states that about one of every 1,600 Caucasian infants is born with the disease. It is much rarer in African Americans, affecting one in every 17,000 infants, according to the AAP.
  • Tay-Sachs disease. A degenerative metabolic and genetic condition most common in people of European Jewish descent. This disease causes brain damage and often leads to blindness, seizures, dementia and paralysis. It is eventually fatal.
  • Turner syndrome. Occurs when one of the two X chromosomes normally found in females is missing or incomplete. It does not affect males. Common symptoms include short stature and absent or delayed puberty.
  • Fragile X syndrome. A condition characterized by mental impairment, autistic-like behaviors, hyperactivity and attention problems. According to the AAFP, it occurs in about one in every 2,000 male infants and around one in every 4,000 female infants.
  • Gastrointestinal defects. Birth defects that may occur in the digestive tract. They often cause obstructions or blockages and typically require surgical treatment. An example of a gastrointestinal defect is imperforate anus, in which the opening at the end of the digestive tract is missing or closed.

Other genetic disorders include the bleeding disorder hemophilia, achondroplasia (the most common form of dwarfism) and muscular dystrophy. Many genetic disorders include metabolic abnormalities. These birth defects are characterized by an inability to produce, use, or transport a body chemical (e.g., enzyme, protein). Around one in every 3,500 infants is born with metabolic abnormalities, according to the March of Dimes. One example of a metabolic abnormality is phenylketonuria (PKU), in which protein is not properly processed and builds up in the blood and tissue. It leads to mental retardation if left untreated, but early treatment with a special diet that is low in phenylalanine (an essential amino acid) can be used to prevent brain damage.

Many birth defects or groups of birth defects that tend to occur together (syndromes) are defined by their cause. Some of these include:

  • Fetal alcohol syndrome. May occur in an infant whose mother consumed alcohol during pregnancy, especially in early pregnancy. Features include mental retardation, problems in the central nervous system (CNS), and abnormalities of the facial features. According the March of Dimes, about one out of every 1,000 infants is born with fetal alcohol syndrome.
  • Rhesus (Rh) disease of the newborn. Occurs when the mother’s blood is incompatible with the blood of the fetus. Features include jaundice, anemia and brain damage. If not treated, this condition can result in the death of the infant. Treatment involves injections of a special blood product (immunoglobulin-Rhogam) at 28 weeks into pregnancy and after the delivery of the infant. About 4,000 infants are born each year with this condition, according to the March of Dimes.

This entry was posted on Wednesday, October 15th, 2008 at 4:08 am and is filed under Articles. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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