Definition of Amniotic constriction bands:

Amniotic constriction bands are strands of fluid-filled sacs that surround a baby in the womb. They may cause a congenital (present from birth) deformity of the arms, legs, fingers, or toes.

Causes, incidence, and risk factors:

Amniotic constriction bands are caused by a type of damage to a part of the placenta called the amnion. The placenta carries blood to a baby still growing in the womb. Damage to the placenta can prevent normal growth development.

Damage to the amnion may produce fiber-like bands that can trap the arms, legs, fingers, or toes of the fetus. These bands reduce blood supply to the areas and cause them to develop abnormally.

Amniotic constriction bands are relatively rare.