Amniotic Band Syndrome

Amniotic band syndrome is caused by strands of the amniotic sac that separate and wrap around the fingers, toes, limbs or other parts of the fetus. This constriction can cause a variety of problems, depending on where the strands are located and how tightly they are wrapped.

Amniotic band syndrome is thought to occur when the inner layer of the amniotic sac, called the amnion, tears without injury to the outer membrane, called the chorion. The developing fetus remains in its fluid-filled sac, but is exposed to the floating tissue from the ruptured amnion. This floating tissue can become entangled around the fetus.

Amniotic band syndrome is rare, occurring in 1 out of every 1,200 to 15,000 live births. The cause of the tearing is unknown, and it is considered a chance event. It does not appear to be genetic or hereditary, and is unlikely to occur in a subsequent pregnancy.

Complications from amniotic band syndrome range from mild to severe. In mild cases, a band may become wrapped around fingers or toes. This can result in amputation of the fingers or toes, or fusion of the fingers or toes (syndactyly). Syndactyly can be treated surgically after birth. Amniotic bands attached to the face or neck can sometimes cause deformities such as cleft lip and palate.

In other instances, a band can be wrapped around an arm or leg, leading to deformities such as a clubbed foot. In more severe cases, an amniotic band can become extremely constrictive, decreasing the blood supply and possibly leading to amputation of the limb.

In the most severe and life-threatening cases, the band wraps around vital areas such as the head or umbilical cord. This can result in fetal death.

The individual strands are small and often hard to see on an ultrasound. Amniotic band syndrome is typically detected indirectly, due to constrictions and swelling in limbs or other parts of the fetus's body.

If there is evidence of amniotic bands, a detailed ultrasound should be performed to assess the severity and avoid a misdiagnosis. Because the strands are difficult to detect by ultrasound, it is important to have your case reviewed by someone knowledgeable in amniotic band syndrome.

In mild cases, fetal surgery is not recommended and any complications are treated after birth with reconstructive surgery. However, all cases of amniotic band syndrome should be monitored to make sure the condition doesn't worsen.

More severe cases may be considered for fetal surgery if the risks to the mother and fetus are small. A full evaluation is required before proceeding with fetal surgery, as each case of amniotic band syndrome is unique and there may be additional complications to consider.

Fetal surgery may be offered if the band is wrapped around a limb and causing swelling and obstructed blood flow. During the surgery, fetal surgeons enter the uterus with a small instrument and attempt to cut the band around the limb, either with a laser or a sharp instrument. The UCSF Fetal Treatment Center has successfully released an amniotic band on a patient's leg to avoid an in-utero amputation of the limb.

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Reviewed by health care specialists at UCSF Benioff Children's Hospital.

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San Francisco, CA 94158
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