In rare cases, amniotic bands become entangled around the fetus. The condition is called amniotic band syndrome. The bands can wrap around limbs, vital areas or the umbilical cord. As the fetus grows, blood flow is restricted.

What Causes Amniotic Band Syndrome?
The fetus floats freely in a liquid-filled sac located inside the uterus. There are two layers to the amniotic sac. The innermost layer is the amnion and the outermost layer is the chorion. A tear or rupture of the amnion is thought to be the cause of amniotic band syndrome. When the innermost sac ruptures, amniotic bands float in the amniotic fluid. These bands can become entangled around the fetus. At first, the fetus’s small size prevents problems, but as the fetus grows, the bands can restrict blood flow.

Blood flow restriction can cause cosmetic damage to fingers, toes, limbs and other body parts, including syndactyly. Syndactyly is a webbing of the fingers or toes resulting in a claw-like appearance. In extreme cases, amputation of fingers, toes or limbs may occur in-utero. If the bands wrap around parts of the neck or face cleft palate or cleft lip may develop. Restriction of the umbilical cord or vital areas like the head can result in death.

Is My Fetus At Risk?
There is no known cause for the amnion rupture or tear. Amniotic band syndrome occurs in up to 1 in 1,200 pregnancies. There does not appear to be a genetic connection, so the condition is not passed between generations. If amniotic band syndrome occurs in one pregnancy, there is no increased risk of the condition in subsequent pregnancies.

How is Amniotic Band Syndrome Detected?
Amniotic band syndrome may be detected during a pregnancy ultrasound, though the amniotic bands are extremely thin making detection difficult. If amniotic band syndrome is suspected, experts suggest an ultrasound with a technician or doctor familiar with the condition. In severe cases, the fetus may show signs of distress leading doctors to order a detailed ultrasound.

Can the Amniotic Band Syndrome be Treated Prior to Birth?
If amniotic band syndrome causes an immediate threat to the fetus, doctors may order surgery to remove the amniotic band restriction, but surgery on the fetus is rare. Most often, cosmetic surgery will be scheduled after birth to correct functional problems resulting from the restriction. After function is restored, parents may choose to schedule additional surgeries to improve cosmetics. Surgery is not required in all cases.