Amniotic Band Syndrome 

What is amniotic band syndrome?

Amniotic band syndrome is a broad term for a group of congenital (present at birth) abnormalities caused 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. Because amniotic band syndrome can result in a wide range of disorders it can be referred to by a variety of names.  Below is a list of names used to describe some of the disorders that are the result of amniotic bands. Your physician may have used one of these names to describe the disorder that your baby is suspected of having. 

Terms applied to defects that are the result of ABS include:

• Amniotic band disruption complex or 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, but it still may be functional.
• Amniochorionic meso-blastic fibrous strings or constriction ring syndrome are other terms that are used 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 that is due to amniotic bands.
• Aberrant tissue bands is another term for amniotic band syndrome.
• Limb and/or body wall defect (LBWD); body stalk complex; amniotic deformity, adhesions, and mutilations (ADAM complex); and amniotic adhesion malformation syndrome are all names used to refer to a similar complex of deformities that usually are fatal. This form of ABS has severe fetal deformities. It is thought to occur early in gestation and alters the development of multiple systems. This disorder is defined by a fetus who has at least two of three findings:
  1. Myelomeningocele (spina bifida) and/or caudal (sacral area or upper buttocks/lower back) regression (did not develop fully).
  2. Thoracoschisis (thoraco means chest and schisis means a cleft or split) and/or abdominoschisis (abdomino refers to abdominal area).
  3. 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.
• Streeter bands is another term for amniotic band syndrome and refers to the name of a physician named Streeter who identified and studied amniotic band syndrome in the first half of the 1900s.

~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 and are 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, 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 cause death for the baby if it becomes too tight.
• More complex pattern of defects designated as limb-body-wall complex. 

The presence of bands is not necessary for the diagnosis of ABS when disorders commonly associated with ABS are found. Likewise, seeing bands on ultrasound without the presence of birth defects is not diagnosed as amniotic band syndrome. 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, anencephaly that is not caused by ABS will not have any skull bone present. However, anencephaly as the result of ABS may have some skull bone remaining, especially near the base of the skull or eye orbits. A typical encephalocele is seen in the midline. Those noted with ABS are off the midline. This same phenomena is true of the other broad categories of malformations related to ABS. The craniofacial defects are commonly associated with nasal deformity and asymmetry and potential limb deformities.

The incidence of ABS is difficult to determine because it 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.

The cause of ABS is unknown, 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 can also occur later in the pregnancy, but this is more commonly seen as the result of an amniocentesis or fetal surgery. When it occurs later in the pregnancy, it often has no effect on the baby. 

We do not know the cause of amniotic bands but we do know it is not caused by anything the mother did or did not 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. The diagnosis is usually made by looking at the birth defects caused by ABS. ABS may be suspected even if your physician cannot see the bands. The appearance of an aberrant sheet or band of amnion attached to the fetus with a deformity and restriction of motion provides a specific diagnosis of ABS. However, the presence of bands is not needed for the diagnosis of ABS if the baby has birth defects that are linked of this syndrome. Likewise, seeing bands without the presence of a birth defect does not result in a diagnosis of ABS.

If your obstetrician suspects ABS, he or she llikely will refer you to a specialist that handles high-risk pregnancies. These doctors are called perinatologists. A targeted ultrasound will be performed to look for deformities.

How does amniotic band syndrome affect my baby?

ABS has a wide range of potential affects. The disorder(s) can range from very minor to lethal. The most common defects associated with this syndrome involve the extremities. The extremities can have defects ranging from minor constriction rings of a digit(s) to constriction rings of an arm and/or leg, lymphedema (swelling) of an extremity beyond the band, amputation of digit(s), arm and/or leg, clubfeet, and/or clubhands. Other deformities seen beyond the extremities can include anencephaly, encephalocele, clefting of face, asymmetric face, spinal deformities and abdominal wall disorders. Some babies have more than one defect. The affects of ABS are a result of how the bands have interrupted development of the various parts of the baby. Those most severely affected will have deformities that cannot be repaired and will not survive. Treatment options for those most severely affected are either ending the pregnancy or palliative care. 

How does amniotic band syndrome affect my pregnancy?

If ABS is suspected, your physician likely will refer you to a specialist who handles high-risk pregnancies. These physicians are perinatologists. A targeted ultrasound will be performed by the perinatologist to confirm the diagnosis and look for birth defects.  An amniocentesis is not usually necessary with this diagnosis if it is a clearcut case. However, in some cases, ABS may be suspected but not confirmed and an amniocentesis may be offered. 

A fetal echocardiogram may be recommended to rule out any associated heart defect.  A fetal echocardiogram is an ultrasound of the baby's heart. Particular attention is paid to the structure, blood flow and valves. This test is especially important if the banding has affected the abdominal wall. This fetal echocardiogram will be done by a pediatric cardiologist. Other specialists you may see during your pregnancy can include a neonatologist, orthopedic surgeon and/or pediatric surgeon, as well as others depending on what disorder(s) are noted. For example, if there is clefting of the lip and/or palate, a plastic surgeon and the craniofacial team/plastic surgery will be consulted before the baby is born. This consultation is to discuss treatment for this specific disorder. A plan of care will be set up for after the baby is born. When a neural tube defect is noted, the spina bifida team/neurosurgery team will be consulted for the same purpose. A  plan of care for after the birth of the baby will be discussed.

ABS usually does not pose any increased risk for the mother. The pregnancy should progress normally. The delivery process is not altered except for the usual reasons. These pregnancies are at a slightly increased risk for premature labor and delivery. 

How is amniotic band syndrome treated?

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 the baby is born, it is recommended that the baby be born at a tertiary care center with subspecialists who can care for the infant. Subspecialists who may be involved in the care of these babies include neonatologists, pediatric surgeons, orthopedic surgeons and plastic surgeons.

Rarely this condition may qualify for experimental fetal surgery. Fetal surgery is used in rare cases in which the bands are constricting the umbilical cord and threatening to cut off the baby's circulation. If the circulation through the umbilical cord is cut off, the 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 and risk of infection for the mother as well as the risks that come with any surgery. Limb amputation is devastating, but it is not life threatening.

What about after surgery?

The surgery needed to correct the defects caused by ABS will have the same risks as any other surgery. There are risks linked to anesthesia, bleeding and infection, and the results may not be as good as expected. Care of your infant will depend on the type of surgery that is required. 

Surgery before birth,  like any surgery, poses a risk of bleeding and infection which can lead to complications for both the mother and baby. Other potential complications related to fetal surgery include inability to completely remove the amniotic band, injury to the baby and premature labor and delivery.

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.

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 questions. Your milk will be frozen and stored in the Neonatal Intensive Care Unit until your baby is ready for it. The Neonatal Intensive Care Unit at Children's Hospital of Wisconsin has breast pumps and private rooms available for you to use when you are at the hospital. You can bring in pictures, small toys, booties and blankets for your baby while he or she is in the NICU.

What is my baby's long-term prognosis?

The long-term prognosis depends on the severity of the problems caused by 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.  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. Some ABS cases have devastating outcomes with no treatment options except palliative care at the time of delivery.