Amniotic Band Syndrome (ABS)

Amniotic band syndrome (ABS) occurs when the lining of the amniotic sac is damaged during pregnancy, creating fibrous, string-like strands of tissue that entangle the fetus or parts of the fetus and or umbilical cord. Called amniotic bands, these strands may wrap around different parts of the developing body, restricting blood flow and disrupting the baby’s normal growth.

What is Amniotic Band Syndrome (ABS)?

Amniotic band syndrome (ABS) occurs when the lining of the amniotic sac is damaged during pregnancy. This creates string-like strands of tissue t in which the fetus gets tangled. These strands (called amniotic bands) may wrap around different parts of the developing body. This cuts off (constricts) blood flow and keeps the baby from growing normally. The constricted blood flow causes a wide range of birth defects. They can be anywhere from mild to severe malformations, loss of limbs or life-threatening problems.

ABS is also known as amniotic band disruption, amniotic band sequence, constriction ring syndrome and ADAM complex, among many other names.

The congenital disorder is rare. It affects anywhere from 1 in 1,200 to 15,000 live births.

How Does ABS Affect my Baby?

The presence and severity of birth defects depend on where the amniotic bands are located and how tightly they are wrapped. The bands most commonly constrict the limbs, fingers and toes. They can also wrap around the fetus’s head, neck, umbilical cord or vital organs.

Some babies may only have a skin indentation. Others may be born with clubbed feet, fused fingers or toes, a cleft palate or other physical deformities. In the most serious cases, severe constriction can cause congenital amputation (missing limbs) or a blocked blood supply. This can be fatal.

What Causes Amniotic Band Syndrome?

The cause of ABS is not known, but researchers do not think it is genetic. It usually happens when the lining of the amniotic sac is torn during pregnancy.

How is Amniotic Band Syndrome Diagnosed?

ABS is usually diagnosed at birth since the amniotic bands are hard to see on a routine ultrasound. In some cases, however, abnormalities, such as limb malformations, can be seen. If your doctor suspects ABS, they may refer you to a fetal center for more advanced testing and care.

Other diagnostic tests may include:

  • Anatomy ultrasound – to confirm the diagnosis, determine where the bands are located and evaluate blood flow
  • MRI – to assess severity of constriction and abnormalities
  • Fetal echocardiogram – to look at the baby’s heart structure and function

These procedures provide more detailed images and information about your baby’s condition.

How is ABS Monitored and Treated?

Once ABS is diagnosed, your doctors will closely monitor your pregnancy, as well as your baby’s growth and development. Regular ultrasounds will help find changes, risks and possible problems so you and your medical team can develop a plan of care.

Mild birth defects may not need treatment. Some babies will need medical or surgical treatment. This is usually done after the baby is born.  

Treatments after the baby is born include (postnatal):

  • Surgery – Babies may need surgery right after delivery or later in life. When needed, emergency surgery is done to release the constricting bands. Plastic and reconstructive surgery to fix deformities may not be done for months or even years. This gives the baby time to grow.
  • Physical or Occupational Therapy – Some infants will rehabilitative therapies to increase strength and function. The type of therapy depends on the type of birth defect.
  • Prosthetics – Children who have lost a limb may get a prothesis. A prosthesis is an artificial device to replace a missing body part. 3-D printing and other technology have vastly improved these devices. They help children regain limb function as early as 12 to 18 months of age.

Sometimes, however, ABS causes severe or life-threatening damage that must be addressed before the baby is born. For example, an amniotic band may be wrapped around the umbilical cord or is cutting off the blood supply to a limb. In these cases, fetal surgery may be an option. 

A minimally invasive procedure called fetoscopic amniotic band resection is commonly done when in-utero intervention is needed. With the help of ultrasound-guided imaging, a specialized surgeon uses a tiny instrument (with a camera on the tip) to reach the fetus through the mother’s abdomen. The surgeon then cuts the band or bands to release constriction and prevent further harm, such as loss of life or limbs.

It is important, however, to make an informed decision and consider that this surgery carries serious risks. These risks include premature delivery, bleeding and damage to the fetus.

How Will ABS Affect the Long-term Health of my Baby?

Long-term outcomes are different for everyone. They usually depend on the body parts affected and the severity of the condition.

The best outcomes usually involve the limbs and birth defects that can be surgically repaired or addressed with interventions that restore function and do not impact overall health. In the most extreme cases, ABS can cause permanent or life-threating problems.