Amniotic band syndrome

Amniotic band syndrome (ABS) comprises of a wide spectrum of abnormalities which result from entrapment of various fetal parts from a disrupted amnion. Due to the randomness of entrapment, each affected individual has the potential to form a very unique deficit.

The phenomenon is estimated to occur in ~1:1200-1300 live births 1,8.

The exact pathogenesis is not well known although several theories have been proposed.

Exogenous theory

An early disruption of the amnion allows the embryo or fetus to enter the chorionic cavity and contact the chorionic side of the amnion leading to fibrous bands, which entrap the fetal body components.

Endogenous theory 

Occurs as a result of vascular compromise with mesoblastic strings not being a causal agent 4.


The vast majority of cases have a sporadic occurrence 8. In rare situations, it may  be associated with:

There is a massive spectrum of abnormalities depending on what part gets entrapped and at what time of gestation. Features are often asymmetrical. Observable features according to position include:

Head/face entrapment
Truncal entrapment
Extremity entrapment

Limb defects tend to be the commonest 7:

In addition to these defects, actual background amniotic bands may also be detected on ultrasound.

The prognosis is extremely variable dependent on the part that gets entrapped. This can range from normal life expectancy at one extreme in the case of a minor distal limb entrapment to in-utero death if there is anencephaly from head entrapment. There is no recognised recurrence risk for future pregnancies.

The differential is extremely variable dependent on the type of deficit and is best left for individual features.

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Article Information

rID: 10841
Section: Syndromes
Synonyms or Alternate Spellings:
  • Amniotic disruption complex
  • Amniotic band sequence
  • ADAM complex
  • Amniotic deformities adhesion mutilation (ADAM)
  • Constriction band syndrome
  • Congenital constriction band syndrome
  • Congenital constriction ring syndrome
  • Congenital ring constriction syndrome

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