Amniotic band constriction

Overview

Amniotic Band Constriction (ABC), also known as Amniotic Band Syndrome or Constriction Band Syndrome, is a rare congenital disorder caused by strands of the amniotic sac detaching and entangling parts of the developing fetus. These fibrous bands can wrap around limbs, fingers, toes, or other body parts, potentially leading to deformities, restricted growth, or even amputation in utero. The severity of the condition varies widely, ranging from minor indentations on the skin to life-threatening abnormalities.

Causes

The exact cause of amniotic band constriction is not fully understood, but it is believed to result from a disruption in the amniotic sac, which normally protects the developing fetus. When the sac ruptures early in pregnancy, fibrous strands from the amnion can float freely and entangle parts of the fetus.

Two main theories explain the condition:

• Extrinsic theory: Early rupture of the amnion leads to fibrous bands that entrap fetal parts.

• Intrinsic theory: Vascular disruption or developmental defects within the fetus lead to constrictions and malformations.

The condition is considered sporadic and is not inherited. Most cases occur randomly and are not linked to genetic or environmental factors.

Symptoms

The symptoms and severity of amniotic band constriction vary depending on when the bands form during pregnancy and which body parts are affected. Common symptoms include:

Limbs and Digits:

• Indentations or constriction rings around arms, legs, fingers, or toes

• Swelling or lymphedema distal to the constriction

• Amputation of digits or limbs in utero (auto-amputation)

• Syndactyly (fusion of fingers or toes)

Craniofacial and Body Defects (less common but more severe):

• Cleft lip or cleft palate

• Clubfoot

• Abdominal wall defects (e.g., gastroschisis)

• Encephalocele or other brain-related protrusions

Diagnosis

Diagnosis of amniotic band constriction may occur before or after birth:

Prenatal Diagnosis:

• Ultrasound: May detect constriction rings, limb deformities, missing limbs, or floating bands in the amniotic fluid

• Fetal MRI: Occasionally used for detailed imaging of soft tissues and confirming findings

Postnatal Diagnosis:

• Physical examination of the newborn reveals visible constrictions, amputations, or malformations

• Further imaging (e.g., X-ray, ultrasound) may be used to assess bone or vascular involvement

Treatment

Treatment depends on the severity and location of the constrictions and may include both surgical and non-surgical approaches:

Non-surgical Management:

• Physical therapy and occupational therapy for mobility and function

• Prosthetics for limb loss to aid development and independence

Surgical Options:

• Constriction band release: Surgical removal or release of tight bands to restore blood flow and prevent further damage

• Z-plasty or skin grafts: To reconstruct areas of deep indentations or scarring

• Corrective surgery: For associated anomalies like clubfoot or cleft palate

Fetal Surgery (rare):

• In select, severe cases diagnosed in utero, fetal surgery may be performed to release amniotic bands and prevent further damage

Prognosis

The prognosis of amniotic band constriction varies widely based on the location, timing, and severity of the bands:

• Mild cases: With minor constriction rings or cosmetic concerns, the outlook is excellent

• Moderate cases: May require surgery or therapy, but children can lead normal lives with appropriate care

• Severe cases: Involving vital organs or extensive limb loss may lead to significant disability or, rarely, stillbirth

With timely surgical intervention and rehabilitation, many children adapt well and achieve functional independence.