Amniotic Band Syndrome

Pregnancy is a time of great joy for many couples as they await the birth of their child. However, it can also be a stressful time. Fetal growth is a very delicate process.

While things usually proceed fine after the first eight weeks, a number of complications are possible.

Amniotic band syndrome is one of those complications. It’s a rare condition associated with the amniotic sac that can have a number of outcomes that range from mild to life threatening.

We've created this guide to explain what amniotic band syndrome is, how it is diagnosed, possible causes and treatment options.

What Is Amniotic Band Syndrome?

Amniotic band syndrome is a rare congenital disorder that occurs when parts of a fetus are entangled by fibrous strands of the amniotic sac.

The amniotic sac is a bag of fluids in the uterus that holds the fetus. It’s made of two different membranes: the chorion and the amnion.

The amnion layer is the inner membrane. Strands of tissue can separate from this membrane if there is a rupture or tear.

The tissue remains connected to the sac on one end and floats freely in the amniotic fluid. The free-floating strands can then get wrapped around fingers, toes, limbs or the head of the unborn child.

Amniotic band syndrome goes by many names and associated terms that include:

• ABS
• Amniotic bands
• Amniotic band sequence
• Amniotic deformity, adhesions, mutilations (ADAM) complex
• Amnion rupture sequence
• Congenital constriction rings
• Constriction band syndrome
• Limb body wall complex
• Streeter anomaly
• Streeter bands
• Streeter dysplasia

There is also something called innocent amniotic bands ¹. This is when amniotic bands are present but haven’t attached to the fetus and don’t restrict fetal movement or growth.

However, medical studies have associated a higher risk of other complications with innocent amniotic bands.

Another related condition is amniotic sheets or amniotic folds. These are benign fibrous bands that adhere to the fetus but cause no harm.

When Does Amniotic Band Syndrome Occur?

Amniotic band syndrome occurs in utero when tissue strands pull free of the amnion membrane layer. This can happen at any point during pregnancy once the fetus has developed the affected body parts.

An amniotic band 12-week scan can catch the earliest signs of ABS at the end of the first trimester. Sometimes detection occurs later at an amniotic band 20-week scan when the baby’s anatomy is being examined.

Amniotic Band Syndrome Causes

The exact cause of amniotic band syndrome has not yet been identified, and it’s possible that more than one cause exists.

Medical experts believe the root cause of amniotic band syndrome in many cases is a rupture in the amnion layer of the sac. Why and how the tear occurs is unknown in many cases and most likely occurs by complete chance.

There is evidence that trauma to the placenta or abdominal area during pregnancy can cause amnion layer tears.

Chorionic villus sampling (CVS), a test in the first trimester that looks for chromosomal defects, can also increase the risk of tearing. Estimates put the risk at 1 in 2,000 CVS procedures.

Using the drug misoprostol after 6-8 weeks of pregnancy has been shown to increase the risk of amniotic band syndrome due to sac tearing. Misoprostol can cause uterine contractions that strain the amniotic sac.

Other theories for the cause have been proposed, some of which are intrinsic (happening within the fetus) and others that are extrinsic (happening outside the fetus) like the ruptured membrane theory. Intrinsic factors involving restricted blood flow ² are believed to be the cause in cases where the amnion layer appears to be intact and when internal organs are affected.

Amniotic band syndrome is associated with what complication in pregnancy?

The only known possible association is tears in the amnion membrane, but what causes those tears is usually not known.

Is amniotic band syndrome inherited?

Amniotic band syndrome isn’t believed to be inherited. It’s thought to be by chance. If it happens in one pregnancy it’s not more likely to happen in the next.

Can amniotic band syndrome be prevented?

Tears in the amnion membrane usually occur by chance and the cause is unknown. Pregnant women should be careful to avoid abdominal injuries since they’ve been shown to increase the risk of tearing.

How Common Is Amniotic Band Syndrome?

Amniotic band syndrome statistics show that the condition is very rare.

It happens in an estimated 1 in 1,200 up to 1 in 15,000 live births.

Who does amniotic band syndrome typically affect?

This condition can happen to any fetus regardless of gender or race. That said, medical research suggests there is a higher risk of ABS:

• During a woman’s first pregnancy
• With problem pregnancies
• Among young women
• Among women of African descent

How Can ABS Affect My Child?

Amniotic band syndrome can affect an unborn child in many ways and every case is unique.

It all depends on how many strands are involved, where the amniotic bands wrap around the fetus and how tightly the bands are entangled. In the vast majority of cases, some sort of deformity is present in the limbs due to restricted movement or blood flow.

How serious is my fetus’s amniotic band syndrome?

The seriousness of amniotic band syndrome can depend on the body part that’s affected and how tightly the fibrous band is wound around the body part.

Amniotic band syndrome of the fingers and toes — The mildest cases of ABS involve the digits. They may need to be amputated or the growth can be stunted in utero.

The fusing of the fingers and toes, a condition known as syndactyly, is also possible. Surgery can be done to correct syndactyly. Extra strands of tissue may also be present on fingers.

Amniotic band syndrome of the foot or leg — If amniotic bands wrap around a leg or foot it can be moderate and cause deformities like club foot or constriction rings. In more severe cases the blood flow to the limb is restricted and amputation is necessary.

Amniotic band syndrome of the hand or arm — Like the foot and leg, if the amniotic bands wrap around an arm or hand, movement is restricted and can cause deformities and/or decreased blood flow. Arms and hands tend to be affected more than legs and feet.

Amniotic band syndrome of the face — It’s also possible for amniotic bands to attach to the face. This can lead to cleft palate and/or cleft lip.

Common Patterns of ABS

There are three common patterns associated with amniotic band syndrome ³:

• Limb-body-wall complex — This is very serious and often lethal due to effects on vital organs.
• Craniofacial abnormalities — The abnormalities include underdeveloped eyes, narrowed nasal passages, facial clefts, misshapen skull and cleft palate. Amniotic band anencephaly is the name of the condition when major parts of the brain, scalp and skull are impacted.
• Limb malformations — This pattern is the most common. One or more limbs can be involved.

Is amniotic band syndrome fatal?

In the majority of cases, amniotic band syndrome is not fatal. The condition could become life-threatening for the fetus if bands wrap around the umbilical cutting off blood flow or bind around the baby’s head.

Do innocent amniotic bands cause problems?

Even when amniotic bands don’t wrap around the fetus it could increase risks during pregnancy. A medical study using ultrasound records from Kings County Hospital Center and the State University of New York Health Science Center at Brooklyn found that the presence of innocent amniotic bands can increase the risk of low birth weight (less than 2,500 grams) and preterm delivery (birth prior to 37 weeks gestation).

Diagnosis of Amniotic Band Syndrome

The number one question for mothers is, how do you diagnose amniotic band syndrome? ABS is diagnosed during pregnancy or shortly after birth.

If there is evidence of ABS during a routine prenatal checkup your medical team should conduct more testing to verify amniotic band syndrome.

How do doctors test for amniotic band syndrome?

Because amniotic band syndrome is so rare and not inherited, doctors do not routinely test specifically for ABS. However, signs of the condition may be discovered while doing other tests.

Can you see amniotic band syndrome in an ultrasound?

Yes, amniotic band syndrome and innocent amniotic bands can be detected with an ultrasound ⁴. If amniotic band syndrome is suspected a detailed, high-resolution ultrasound will be done to diagnose the condition and assess the severity including the affected areas of the body and number of strands involved.

Genetic Tests for Amniotic Band Syndrome - Are They Available?

Because amniotic band syndrome isn’t believed to be hereditary there are no genetic tests for the condition.

However, there is current research exploring the possibility of a genetic connection ⁵in cases of intrinsic amniotic band syndrome. Most likely, if a genetic factor is present it’s a genetic predisposition, which means a trigger is needed for the condition to occur.

Amniotic Band Syndrome Management and Treatment

Once amniotic band syndrome is confirmed, the pregnancy will be closely monitored.

Additional ultrasounds will be performed to monitor the situation and look for signs that the condition is becoming more severe. Amniotic band second-trimester monitoring is extremely important because the fetus is undergoing rapid development.

Whether additional steps are taken to manage ABS during pregnancy depends on the severity of the situation.

Fetal Surgery for ABS

Fetal surgery is not a standard treatment for amniotic band syndrome. It’s only recommended in the most severe cases when ABS is life-threatening.

Risks to both the fetus and mother are carefully considered to determine if surgery is the best course of action. Typically, doctors prefer to do reconstructive surgery after birth if needed.

If the bands are wrapped around the umbilical cord, head or a limb and are restricting blood flow, it could warrant fetal surgery. The surgeon enters the uterus and can cut the band free using a laser or sharp instrument.

What are my choices during this pregnancy?

When detected early, expectant mothers have the choice to monitor the condition, terminate the pregnancy if the condition is severe and not expected to sustain life or have fetal surgery if the benefits outweigh the potential risks to the mother and fetus.

What will happen after birth?

What happens after birth depends on the severity of the condition. In minor cases no follow up care may be needed. Some babies will require reconstructive surgery soon after birth to correct deformities.

This can include surgery to correct fused digits, club foot or cleft palate. Usually, surgery is performed by a pediatric plastic surgeon.

Related medical procedures may be needed years down the line to treat amniotic band syndrome pain or help with mobility and dexterity. Physical therapy is common to help infants and children improve the use of their limbs, hands and feet.

Supportive treatments may also be needed depending on the complications.

The Prognosis for Amniotic Band Syndrome

The first thing expectant mothers should know is that amniotic band syndrome does not impact a mother’s health at all. Only the fetus is impacted by the condition.

A prognosis can be made during pregnancy, but typically complications are dealt with after birth. Only then can a truly accurate prognosis be made.

What is the outcome for a fetus with amniotic band syndrome?

If fetal surgery is required the overall survival rate is 74%. The prognosis is better in cases that don’t have umbilical cord involvement.

Can amniotic band go away?

Ultrasounds have shown that many benign amniotic bands do go away. Up to 70% aren’t present on future ultrasounds.

If amniotic band syndrome causes serious deformities it can be difficult to deal with. Joining an amniotic band forum can provide both information and support.

The Amniotic Band Syndrome Support Group is an invaluable resource for parents.

It’s also important for parents to familiarize themselves with the condition as much as possible. Resources like the amniotic band syndrome ppt from Brightwood College provides easy to understand explanations for ABS and its effects.

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