Human disease
Congenital amputation is birth without a limb or limbs, or without a part of a limb or limbs.
It is known to be caused by blood clots forming in the fetus while "in utero" (vascular insult) and from amniotic band syndrome: fibrous bands of the amnion that constrict fetal limbs to such an extent that they fail to form or actually fall off due to missing blood supply. Congenital amputation can also occur due to maternal exposure to teratogens during pregnancy.
Causes.
The exact cause of congenital amputation is unknown and can result from a number of causes. However, most cases show that the first three months in a pregnancy are when most birth defects occur because that is when the organs of the fetus are beginning to form. One common cause is amniotic band syndrome, which occurs when the inner fetal membrane (amnion) ruptures without injury to the outer membrane (chorion). Fibrous bands from the ruptured amnion float in the amniotic fluid and can get entangled with the fetus, thus reducing blood supply to the developing limbs to such an extent that the limbs can become strangulated; the tissues die and are absorbed into the amniotic fluid. A baby with congenital amputation can be missing a portion of a limb or the entire limb, which results in the complete absence of a limb beyond a certain point where only a stump is left is known as transverse deficiency or amelia. When a specific part is missing, it is referred to as longitudinal deficiency. Finally, phocomelia occurs when only a mid-portion of a limb is missing; for example when the hands or feet are directly attached to the trunk of the body.
Amnion ruptures can be caused by:
Congenital amputation is the least common reason for amputation, but a study published in "BMC Musculoskelet Disorders" found that 21.1 in 10,000 babies were born with a missing or deformed limb between 1981 and 2010 in the Netherlands, and the CDC estimates that 4 in 10,000 babies are born in the United States with upper limb reductions and 2 in 10,000 with lower limb reductions. During certain periods in history, an increase in congenital amputations has been documented. One example includes the thalidomide tragedy that occurred in the 1960s when pregnant mothers were given a tranquilizer that contained the harmful drug, which produced an increase in children born without limbs.
Diagnosis.
For most cases the diagnosis for congenital amputation is not made until the infant is born. One procedure that is helpful in determining this condition in an infant is an ultrasound examination of a fetus when still in the mother's abdomen as it can reveal the absence of a limb. However, since ultrasounds are routine they may not pick up all the signs of some of the more subtle birth defects.
Treatment.
The most popular method of treatment for congenital amputation is having the child be fit for a prosthesis which can lead to normal development, so the muscles don't atrophy. If there is congenital amputation of the fingers, plastic surgery can be performed by using the big toe or second toes in place of the missing fingers of the hand.
In rare cases of amniotic banding syndrome, if diagnosed "in utero", fetal surgery may be considered to save a limb which is in danger of amputation.
References.
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Further reading.
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