Amniotic band syndrome

What is amniotic band syndrome (ABS)?

Amniotic band syndrome is a broad term for a group of congenital abnormalities that occur when bands of amnion (the inner lining of the amniotic sack or "bag of water") peel away from the sack and attach or wrap around parts of the baby's body, disrupting normal development. 

ABS can cause a wide range of disorders. Below is a list of some of the disorders that are the result of amniotic bands. Your physician may have used one of these names to describe the disorder he or she suspects your baby might have.

Terms applied to defects that are the result of ABS:

  • Amniotic band disruption complex and amniotic disruption complex refer to deformities of any area of the fetus. The band can wrap around a body part and stop the part from completely forming. Although the affected body part may not form completely or normally, it may still be functional. 
  • Amniochorionic meso-blastic fibrous strings and constriction ring syndrome are other terms that experts use to describe amniotic band syndrome. These terms usually refer to issues related to bands that wrap around a limb, digit or even the umbilical cord. 
  • Transverse terminal defects of limb refers to amputation or malformation of part or all of a limb due to amniotic bands.
  • Aberrant tissue bands is another term for amniotic band syndrome. 
  • Streeter bands is another term for ABS. It refers to a physician named Streeter who identified and studied amniotic band syndrome in the first half of the 1900s. 

There are several forms of ABS that cause severe fetal deformities: 

  • Limb and/or body wall defect (LBWD)
  • Body stalk complex
  • Amniotic deformity, adhesions and mutilations (ADAM complex)
  • Amniotic adhesion malformation syndrome 

All of these deformities usually are fatal. Experts believe they occur early in the pregnancy and they alter the development of multiple body systems. These disorders are defined by a fetus who has at least two of three findings: 

  • Myelomeningocele (spina bifida) and/or caudal (sacral area or upper buttocks/lower back) regression 
  • Thoracoschisis (thoraco means chest and schisis means a cleft or split) and/or abdominoschisis (abdomino refers to abdominal area) 
  • Limb deformities
  • Congenital amputation refers to amputation of a part of the fetus, usually a limb. This means that the limb did not develop at all.

How can ABS affect my child?

ABS can cause a wide variety of birth defects. These deformities can be relatively minor, involving a finger, toe or minor constriction rings (snug bands of the amnion wrapped around a body part). More severe cases may involve multiple body systems. These severe cases are usually fatal. 

The birth defects that can occur as a result of ABS fit into the following broad categories: 

  • Neural tube defects (anencephaly, myelomeningocele, acrania, cephalocele) 
  • Craniofacial defects (clefting of lip, palate or face; asymmetric face) 
  • Limb defects (amputations, joint contractures {the joint does not move freely}, clubbing of feet/hands )
  • Constrictive bands (swelling of limb beyond the constriction); this can also affect the umbilical cord, which can be life-threatening for your baby
  • Limb-body-wall complex is a more complex pattern of defects

Do bands and ABS always go hand in hand?

The presence of bands is not necessary for the diagnosis of ABS when doctors find disorders commonly associated with ABS. And, the presence of bands on an ultrasound without associated birth defects does not lead to a diagnosis of ABS. 

Some of the defects typically associated with amniotic band syndrome also can occur without ABS. However, there are some signs that indicate these disorders are a result of ABS.

For example, a child with anencephaly that is not caused by ABS will not have any skull bone present. However, if the anencephaly is a result of ABS, the child may have some skull bone remaining, especially near the base of the skull or eye orbits. 

A typical encephalocele occurs in the midline. Encephaloceles that occur with ABS are off the midline. This same phenomena is true of the other broad categories of malformations related to ABS. The craniofacial defects often involve nasal deformity, asymmetry and potential limb deformities.

How common is ABS?

The incidence of ABS is hard to determine because ABS is difficult to diagnose. Estimates vary widely due to the difficulty in accurate diagnosis. Reported incidence varies from 1 in 1,200 to 1 in 15,000 live births. The incidence in miscarriages may be as high as 178 in 10,000. 

What causes ABS?

Experts do not know what causes ABS, but there are several theories. The most widely accepted theory is the rupture of the amnion early in gestation, between 28 days after conception to 18 weeks gestation. The fibrous bands of amnion that result from this rupture can wrap around the limbs, resulting in tourniquet-like defects and amputations. This also can occur later in the pregnancy, but this is more commonly seen as the result of an amniocentesis or fetal surgery. When ABS occurs later in the pregnancy, it often has no effect on the baby. 

Although we do not know the cause of amniotic bands, we do know it is not caused by anything mothers do or don’t do during pregnancy. 

Prenatal diagnosis of amniotic band syndrome

The earliest detection of ABS by ultrasound has been at approximately 12 weeks gestation. The bands themselves are difficult to see on ultrasound, so doctors usually make the diagnosis by looking at birth defects caused by ABS. 

Your doctor may suspect ABS even if he or she cannot see the bands. If your obstetrician suspects ABS, he or she will likely refer you to a maternal-fetal medicine specialist (a specialist who handles high-risk pregnancies). This doctor will perform a targeted ultrasound to look for deformities.

How does amniotic band syndrome affect my baby?

ABS has a wide range of potential effects. The disorder(s) can range from minor to life threatening. The most common defects associated with this syndrome involve the extremities. The extremities can have defects ranging from minor constriction rings of a digit (or digits) to severe issues, including:

  • Constriction rings of an arm and/or leg
  • Lymphedema (swelling) of an extremity beyond the band
  • Amputation of digit(s) or arm and/or leg
  • Clubfeet and/or clubhands

Other deformities seen beyond the extremities can include: 

Some babies have more than one defect. The effects of ABS are a result of how the bands have interrupted development of the various parts of the baby. Children most severely affected will have deformities that cannot be repaired. These deformities will eventually lead to death. 

How does amniotic band syndrome affect my pregnancy?

There are some tests you may have to undergo if your physician suspects your child has ABS. First, your doctor will likely refer you to a maternal-fetal medicine specialist (a specialist who handles high-risk pregnancies). That specialist will order additional tests and will assist in your care.

Tests may include:

Targeted ultrasound

The first test the maternal-fetal medicine specialist will perform is a targeted ultrasound. This is to confirm the diagnosis and look for birth defects. 

Amniocentesis

An amniocentesis is not usually necessary with this diagnosis if it is a clear-cut case. However, in some cases, ABS may be suspected but not confirmed. Your doctor may suggest amniocentesis to help with the diagnosis. 

Fetal echocardiogram

Your doctor may recommend a fetal echocardiogram to rule out any associated heart defect. This is an ultrasound of your baby's heart. During the test, the doctor will pay particular attention to the structure of the heart, along with the blood flow and the valves. This test is especially important if the banding has affected the abdominal wall. 

If your baby has a fetal echocardiogram, it will be performed by pediatric cardiologist. 

Will I have to see other specialists if my baby has ABS?

  • Other specialists you may see during your pregnancy are:
  • A neonatologist
  • An orthopedic surgeon
  • A pediatric surgeon
  • Other specialists, depending on what disorders are found during the exams
    • For example, if there is clefting of the lip and/or palate, we will consult with a plastic surgeon and the craniofacial team/plastic surgery before your baby is born. This consultation is to discuss treatment for this specific disorder. Your doctors will set up a plan of care for after your baby is born. 
    • When a neural tube defect is noted, we will consult the spina bifida team/neurosurgery team for the same purpose. Your doctors will discuss a plan of care for after the birth of your baby.

Does ABS put me at risk?

ABS usually does not pose any increased risk for the mother. If your child has ABS, your pregnancy should progress normally. The delivery process will not be altered, except for the usual reasons. 

There is a slightly increased risk that your baby will be born prematurely. 

How do you treat amniotic band syndrome?

There is a wide range of potential affects resulting from ABS. Some are very minor, while others can be life threatening or fatal. The majority of babies affected by amniotic band syndrome require treatment after delivery. Many have minor digit or limb defects that will have no impact on survival but will require follow-up by a pediatric subspecialist. A thorough physical exam after birth will assess the severity of the problems caused by ABS. 

In cases where ABS is found before your baby is born, we recommend that your baby be born at a facility with subspecialists who can care for your child immediately after delivery. 

Subspecialists who may be involved in the care of babies with ABS include: 

  • Neonatologists
  • Pediatric surgeons
  • Orthopedic surgeons
  • Plastic surgeons

Experimental fetal surgery

Rarely, some children with ABS may be candidates for experimental fetal surgery. Doctors perform fetal surgery in rare cases when the bands are constricting the umbilical cord and threatening to cut off the baby's circulation. This is a risk because if the circulation through the umbilical cord is cut off, your baby will die. 

Other times, fetal surgery has been used to save a limb that the bands are threatening to amputate. Use of this procedure for a problem that is not life threatening is controversial. Some argue the surgery is hard to justify for non-life-threatening issues due to the potential of serious complications to the mother and baby. 

These complications include: 

  • The risk of fetal death due to premature delivery
  • Risk of infection for the mother
  • Risks that come with any surgery

Limb amputation is devastating, but it is not life threatening. 

Risks of fetal surgery

The surgery needed to correct the defects caused by ABS carries the same risks as any other surgery. For example, there are risks linked to:

  • Anesthesia
  • Bleeding
  • Infection

Risks that apply specifically to fetal surgery for ABS are:

  • Inability to completely remove the amniotic band
  • Injury to the baby
  • Premature labor and delivery

Additionally, there is a chance that the results may not be as good as expected. Care of your infant after surgery will depend on the type of surgery performed. 

Surgery after birth

Most of the time, we wait until after your baby is born to perform surgery to treat ABS. There are risks for those surgeries as well, but we do not perform surgery on our patients unless we believe (and the parents agree) that the risks outweigh the benefits.

Will I be able to help care for my baby after surgery?

Yes. Please ask your baby's nurse about ways to interact with and care for your baby after surgery. 

Breastfeeding your baby after surgery

If you planned to breastfeed your baby, you can begin to pump your breasts and freeze the breast milk while you are still in the hospital. A lactation consultant can help answer your questions. Your milk will be frozen and stored in the Neonatal Intensive Care Unit until your baby is ready for it. 

The NICU at Children's Hospital of Wisconsin has breast pumps and private rooms available for you to use when you are at the hospital. 

What is my baby's long-term prognosis?

The long-term prognosis depends on the severity of the problems caused by the ABS. There is excellent long-term outcome for babies with only the limbs affected, even in the case of amputation. 

Advances in pediatric surgery now provide excellent results and prognosis for craniofacial disorders, such as cleft lip and palate. However, some babies may be disfigured despite these advances. 

Abdominal wall defects with free-floating bowel usually have excellent results. However, in cases where other internal organs are exposed, the prognosis may be more guarded. 

Unfortunately, some ABS cases have devastating outcomes with no treatment options except palliative care at the time of delivery.