Amniotic Band Syndrome

The amniotic sac is the intrauterine bag-like structure in which a fetus develops. This sac has an outer covering called chorion and an inner membrane called amnion. In some cases, the amnion ruptures and the chorion remains intact. When the amnion ruptures, many strands/bands of tissues of the ruptured amnion, float in the amniotic fluid along with the fetus. These bands can get entangled in the limbs or other parts of the fetus. These bands do not grow with the fetus, resulting in the tightening of their grip, which constricts blood flow to that body part and causes deformities. The type and severity of the deformity depends on the location of the bands and the manner of entrapment. This type of congenital disorder has different names, such as amniotic band constriction, amniotic band sequence, Streeter dysplasia, congenital constriction bands or rings, and amniotic deformity adhesions mutilations (ADAM).

Consequences

Amniotic band syndrome or ABS is characterized by both mild and severe deformities. In some cases, the bands get entangled with the fingers or toes of the fetus and results in partial or total webbing (fusion of fingers or toes). This condition is called syndactyly of the fingers or toes and can be rectified through surgery. The severe form is the amputation of fingers or toes due to the entwining of the bands. This can occur in the fetal stage itself, but in some cases, the restriction of blood supply results in dead (necrotic) limbs, which are amputated after the birth of the baby.

The amniotic bands can entrap the arms, legs or digits (finger or toe) and form ring-like patterns called constriction rings around these parts. It can also cause swelling of the extremities. If the band is attached to the face or neck, it can cause deformities, like, cleft lip and cleft palate. Amniotic band entrapping the head, umbilical cord or other such vital parts may cause severe complications and may even lead to death of the fetus. The deformities caused by amniotic band syndrome depend on the location and extent of constriction. Fortunately most ABS complications are handled after birth through reconstructive surgery to correct fused fingers and toes, cleft lip, constriction grooves etc.

Diagnosis

Diagnosis of this condition is difficult before birth, as these strands are too small to be visible on ultrasound. In many cases, amniotic band syndrome is detected through its effects on the fetal body, like swelling, amputation, etc. Normally, the rupture of the amnion occurs between 28 days to 18 weeks of conception, but in some cases, it can happen at a later stage too.

Treatment

The most common treatment of amniotic band syndrome is reconstructive or plastic surgery done after birth to rectify the deformity. Long term physical or occupational therapy is also recommended. If amniotic band syndrome is detected during the fetal stage itself, fetal surgery is conducted in rare cases, to save the baby from deformity. This surgery is not performed, if the umbilical cord or any vital organs are involved. Usually, fetal surgery is performed after completion of the seventh month of pregnancy.

Studies show that amniotic band syndrome can cause miscarriages and affects one in 1200 live births. Almost 50 percent of the congenital deformities include cleft lip, cleft palate and clubfoot and 80 percent of the abnormalities involve hands and fingers. Amniotic band syndrome is not hereditary and there is no known cause for its occurrence. It is only accidental and if there are any signs of amniotic band syndrome, like swelling on limbs, digits, etc. observed on the ultrasound test, then further detailed tests should be done to establish amnion tearing as the cause. Other than this there are no preventive measures as such.