Amniotic Band Syndrome

Amniotic band syndrome (ABS; amniotic constriction band sequence, limb body wall complex in the severe form) is a set of congenital anomalies due to entrapment of fetal parts by fibrous bands. The bands arise from rupture of the amnion with fetal entanglement (extrinsic theory) or from a vascular disruption within the fetus (intrinsic theory). Incidence is about 1 in 1,200 to 15,000 live births.

Associations: oligohydramnios, early amniotic rupture (after amniocentesis, chorionic villus sampling, fetoscopic procedures; iatrogenic ABS), connective tissue disease (Ehlers-Danlos), trauma, and prematurity. Consequences vary from simple constriction rings to lethal craniofacial and body wall defects.

• Constriction rings of limbs or digits (commonest, 80 to 90%), with distal lymphoedema, intrauterine amputations, and acrosyndactyly (distal fusion with proximal sinus)
• Club foot (about 30%), limb length discrepancy, pseudarthrosis of the tibia
• Craniofacial: clefts (asymmetric, atypical clefts of the lip, palate, and face), encephalocele, anencephaly like defects
• Body wall defects (limb body wall complex): thoracoschisis, abdominoschisis, with evisceration, scoliosis, and cord adhesion
• Neonatal compromise in neurovascular compression of distal limbs; fetal demise in severe forms

• Prenatal ultrasound: thin echogenic bands within the amniotic cavity attached to the fetus, constricted limbs with distal oedema, asymmetric defects, abnormal fetal position fixed, amputations, and craniofacial or body wall defects. 3D ultrasound and fetal MRI help. Diagnosis in the first trimester is possible in severe cases
• Differential: amniotic sheets or uterine synechiae (the fetus is not attached and membrane has a thick base), chorioamniotic separation, and non-disruptive anomalies (such as isolated clubfoot)
• Genetic evaluation: karyotype or microarray for associated anomalies; connective tissue disease testing when indicated
• Postnatal: clinical evaluation, radiographs, and vascular assessment of affected limbs

• Antenatal:
  • Detailed anomaly scans, counselling, serial ultrasound every 2 to 4 weeks for assessing limb perfusion (Doppler), growth and fluid.
  • Fetoscopic amniotic band release (laser or scissor) in selected cases with progressive limb constriction and distal oedema before 28 weeks to prevent amputation (experimental; risks include PPROM and preterm birth).
  • Termination or palliative care for lethal anomalies such as limb body wall complex.
• Delivery at a tertiary centre; mode by obstetric indication; paediatric surgery and orthopaedic team on standby.
• Postnatal management:
  • Surgical release of constriction bands (Z-plasty or multiple Z-plasties) within the first year (urgent in cases with vascular compromise or lymphoedema). Release in staged fashion (half the circumference at a time to protect vascularity).
  • Syndactyly release.
  • Toe-to-hand transfer or microsurgical reconstruction for digit amputations.
  • Clubfoot management with Ponseti casting.
  • Prosthetics, physiotherapy and occupational therapy.
• Counselling: sporadic condition with very low recurrence (about 1% or less); recurrence risk is not increased in most cases.
• Long term: orthopaedic follow up for limb length discrepancy, and psychological support.