Amniotic band syndrome is a rare condition caused when strands of the amniotic sac separate, wrap around, and constrict parts of the fetal body. During pregnancy, the baby floats in amniotic fluid which is contained inside a sac inside the uterus. The amniotic sac is made up of two layers, the outer membrane called the chorion and the inner membrane called the amnion. Amniotic band syndrome occurs when the inner membrane (the amnion) tears, creating free-floating bands of tissue. The outer membrane (the chorion) is undamaged, and the baby remains inside the amniotic sac.
The free-floating bands of tissue can become entangled around the developing baby. The complications from this condition range from mild to severe, depending on where and how tight the bands are wrapped. Mild complications include entanglement of the fingers and toes, which can cause the digits to be fused together by a thin membrane or result in digit amputation. More serious complications include abdominal wall defects, cleft lip, cleft palate, encephalocele, limb amputation, and limb deformity.
This condition is not a fatal diagnosis, but in severe cases, when the bands wrap around vital areas like the head or umbilical cord, it can result in fetal death. Amniotic band syndrome is occasionally diagnosed in conjunction with fatal prenatal conditions such as acrania and body-stalk anomaly.
Amniotic band syndrome is diagnosed and monitored by ultrasound during pregnancy, and there is a high rate of premature birth associated with this condition. Amniotic band syndrome has an incidence rate ranging from 1 in 1,200 to 1 in 15,000 live births.
Most cases of amniotic band syndrome are random; therefore, the recurrence risk is non-existent. For cases in which amniotic band syndrome is correlated to an underlying disorder or an additional diagnosis, the recurrence risk is based on that disorder or diagnosis.