Amniotic band syndrome

Amniotic Band Syndrome occurs when the fetus becomes entangled in fibrous string-like amniotic bands in the womb, restricting blood flow and affecting the baby’s development.

It can cause a number of different anomalies depending on which body part(s) is affected.

The symptoms of amniotic band syndrome depend on the severity and location of the constrictions. The mildest constrictions affect only the superficial skin and may not require treatment. Deeper constrictions may block lymphatic vessels, impair blood flow, and require immediate surgical care. When the bands affect the limbs, the lower part of the limbs are most often involved, especially the middle, long, and index fingers of the hand. When the feet are involved, the bands most commonly affect the big toe.

Pressure from the bands may result in additional abnormalities, such as underdevelopment of a limb, bone abnormalities, amputations, leg-length discrepancy, and club feet. Constriction bands across the head and face may lead to facial clefts. Severe clefts affecting vital organs are often life-threatening. If a band wraps tightly around a limb, the limb can actually be completely amputated. The baby may be born missing fingers, toes, part of an arm or leg. If the band is across the baby’s face it can cause cleft lip and palate. In a large number of cases the baby is also born with clubfeet. ABS is also the cause of numerous miscarriages, such as when a band becomes wrapped around the umbilical cord.

ABS occurs randomly. It’s not genetic, nor is it caused by anything a pregnant Mom did or didn’t do during pregnancy. To date, no prenatal factors have been associated with ABS. It is extremely unlikely that ABS will affect a future pregnancy. Recurrence risk is estimated based upon family history, patient history, and thorough physical examination. Most ABS is sporadic with very low recurrence risk; however, a few familial cases have been reported. Genetic counseling to discuss recurrence risk is recommended if a genetic disease associated with amniotic bands is suspected.

Incidence

The estimated incidence of ABS ranges from 1:1200 to 1:15,000 in live births, and 1:70 in stillbirths. It affects both sexes equally.

What Causes Amniotic Band Syndrome?

Amniotic Band Syndrome is not genetic (i.e. not inherited). It is extremely unlikely that ABS will affect a future pregnancy. To date, no prenatal factors have been associated with ABS. Amniotic bands are caused by damage to a part of the placenta called the amnion. Damage to the amnion may produce fiber-like bands that can trap parts of the developing baby.

The commonly accepted view is that ABS occurs when the inner membrane (amnion) ruptures without injury to the outer membrane (chorion), this exposes the baby to fibrous sticky tissue (bands) from the ruptured amnion which can float in the waters of the uterus, these fibrous tissues can entangle the baby reducing blood supply and causing congenital abnormalities. In some cases a complete “natural” amputation of a digit(s) or limb may occur before birth or the digit(s) or limbs may be necrotic (dead) and require surgical amputation following birth.

A strong relationship between ABS and clubfoot exists. A 31.5% of associated clubfoot deformity and ABS can be correlated with 20% occurring bilaterally. Other abnormalities found with ABS include: clubhands, cleft lip, and/or cleft palate, and hemangioma.

Diagnosis

The earliest reported detection of an amniotic band is at 12 weeks gestation, by vaginal ultrasound. On ultrasound the bands appear as thin, mobile lines, which may be seen attached to or around the baby. However these bands may be difficult to detect by ultrasound, and are more often diagnosed by the results of the fusion, such as missing or deformed limbs.

Effects of Amniotic Band Syndrome

With Amniotic Banding no two cases are exactly alike. There are several features that are relatively consistent: syndactyly (webbed digits), distal ring constrictions, deformity of the nails, stunted growth of the small bones in the digits, limb length discrepancy, distal lymphedema (swelling), and congenital band indentations. If a band wraps tightly around a limb, the limb can actually be completely amputated. If the band is across the baby’s face it can cause cleft palate. In a large number of cases the baby is also born with clubfeet. ABS is also the cause of numerous miscarriages, such as when a band becomes wrapped around the umbilical cord.

Amniotic Band Syndrome – Alternative Names

Some of these are different names for ABS and some are other syndromes that are often confused with ABS. Misdiagnosis is apparently common.

  • Amniotic Deformity, Adhesions and Mutilations
  • Amniotic band disruption complex or sequence
  • Amniotic bands and sheets
  • Annular constriction bands
  • Congenital ring constriction
  • Constriction Band Syndrome and Amniotic Constriction Band Syndrome
  • Intrauterine amputation
  • Streeter’s dysplasia
  • TEARS (The Early Amnion Rupture Spectrum)
  • Congenital Transverse Defects or Deficiency
  • Limb-body Wall Complex

Pregnancy management

The prenatal and intrapartum management of suspected ABS depends on the type and extent of malformations. All patients should receive information about the fetal abnormalities that have been detected, the possibility of additional undetected abnormalities, prognosis, and the option of pregnancy termination. If pregnancy termination is performed, it is useful to try to deliver an intact abortus that can be examined to confirm the diagnosis.

There have been case reports of in utero surgical lysis of constriction rings, purportedly leading to improved blood flow and prevention of amputation. The efficacy of this approach is unproven and selection criteria for candidates for in utero intervention have not been defined

Treatment Options

Treatment depends on which body part the band was wrapped around and the severity of the abnormality it caused. Mild cases may not require treatment, however all bands need monitoring as growth occurs to watch for progressive constriction and swelling. Other constrictions may require surgical management; surgical options will vary depending on the abnormality. People with amniotic band syndrome who have amputations may benefit from the use of prosthetics. In Utero Surgery – has been performed to free limbs from amniotic bands that threaten to amputate limbs.

Between 1965 and 2013, 14 cases of fetoscopic laser transection of amniotic bands around a limb have been reported. Seven infants had an acceptable functional outcome, but some needed additional corrective postnatal surgical procedures. One fetus died in utero. In three cases, intraoperative intra-amniotic bleeding and uterine wall bleeding prevented completion of fetoscopic surgery, but in two of these cases the bands were released under ultrasound guidance. Eight cases were complicated by preterm premature rupture of membranes, which occurred within 24 hours of the intervention in two cases, at four days in one case, and 4 to 13 weeks after the intervention in the remainder. Ten pregnancies delivered preterm.

Postnatal treatment options include surgical intervention to enhance function or for cosmetic purposes, and prosthesis and physiotherapy for individuals with limb defects.

Prognosis

Because the prognosis of people with amniotic band syndrome can vary from patient to patient, the best person to provide your family with information regarding your child’s prognosis, is the health care providers involved in their care. In general, the outlook for infants with a single band involving the superficial skin of the wrist and/or hand is good. While the family and child will need to adjust to the cosmetic difference, the functional use of the hand is normal. Deeper bands can be associated with complications (i.e., blockage of lymph and blood vessels) that can worsen over time and may require surgery. Some people with amniotic band syndrome are born with acrosyndactyly, a fusion of the fingers that may limit the hand function and cause stiffness of the joints. In many cases a good ability to hold and grasp may be obtained with reconstructive procedures

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