Limbs can be missing, deformed, or incompletely developed at birth.
Birth defects, also called congenital anomalies, are physical abnormalities that occur before a baby is born. “Congenital” means “present at birth.” (See also Introduction to Birth Defects of the Face, Bones, Joints, and Muscles.)
Limbs may form abnormally. For example, bones in the hand and forearm may be missing because of a genetic defect (see Chromosome Abnormalities), or sometimes part or all of a hand or foot may be missing. Normal development of a limb can also become disrupted in the womb. In amniotic band syndrome, limbs develop abnormally when they are constricted by thin strands of tissue from the amniotic sac (the sac that holds the amniotic fluid surrounding the developing fetus in the womb).
Abnormalities of the limbs can also be caused by a congenital infection or a teratogen
Abnormalities of the arms and legs may occur in a horizontal fashion (for example, if the arm is shorter than normal) or in a lengthwise fashion (for example, the arm is abnormal on the thumb side—from the elbow to the thumb—but normal on the little finger side).
A child who has one birth defect of the limbs is more likely to have another abnormality.
Diagnosis of Missing or Incompletely Formed Limbs
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Before birth, ultrasonography
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After birth, x-rays
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Sometimes genetic testing
Before birth, doctors are sometimes able to diagnose these defects during an ultrasound.
After birth, doctors typically take x-rays and may do other imaging tests to determine which bones are affected.
Because abnormal genes may be involved in birth defects of the limbs, affected babies should be evaluated by a geneticist. A geneticist is a doctor who specializes in genetics (the science of genes and how certain qualities or traits are passed from parents to offspring). Genetic testing of a sample of the baby’s blood may be done to look for chromosome and gene abnormalities. This testing can help doctors determine whether a specific genetic disorder is the cause and rule out other causes.
Treatment of Missing or Incompletely Formed Limbs
Children often become very adept at using a malformed or artificial limb.
An artificial limb (prosthesis) can often be fitted (usually when the child is able to sit independently) to make the malformed limb easier to use or to replace a limb that is missing or mostly missing. Children use a prosthesis most successfully when it is fitted early and becomes an integral part of their body and body image during the developmental years. During infancy, prostheses should be as simple and durable as possible. For example, a baby can be fitted with a hook rather than a bioelectric arm.
Most children who are born with a birth defect of the limbs lead normal lives.
If an abnormal gene is identified, families of affected children may benefit from genetic counseling.
