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Parents are often devastated when they find out their newborn has a congenital birth defect. An uncommon cause of birth defects includes amniotic bands. Amniotic band sequence (ABS) involves a group of disorders that result in birth defects of the extremities in a developing fetus.

When a fetus is in the womb, a membranous sac filled with fluid surrounds and protects the baby. During ABS, it is thought that the inner sac surrounding the baby, or the amnion, ruptures, leaving behind fibrinous strings in the amniotic fluid. These string-like bands can then wrap around the arms, legs, fingers, and/or toes. As the baby grows, these bands put pressure on the affected body parts.

Most of the time, the bands only affect the outer layers of the soft tissues. In a mild case, they only leave a crease in the skin at the affected area. In more serious cases, however, these bands can cause constriction and cut off blood supply to the affected area, eventually leading to malformations and possibly even amputations.

ABS is a rare disorder, affecting anywhere from 1 in every 1,200 to 15,000 live births. The cause of amniotic bands is not known, but most researchers don’t believe it’s due to a genetic condition. Even after a woman has experienced ABS, it is extremely unlikely for this problem to occur in future pregnancies. ABS is also thought to be a cause of miscarriages, when the bands wrap around the umbilical cord, causing the oxygen supply to the fetus to be cut off.

No two amniotic band birth defects are the same. They can result in anything from an amputated finger or toe to an entire limb. Bands that lie across the face can cause a cleft lip or palate. Often, babies who suffer from amniotic bands are also born with club feet because the band damages the nerve in the leg that controls the lower leg and foot.

Often, a baby will need surgical reconstruction on the affected body part. Recently, in-utero surgery has been performed to loosen the bands in an attempt to save a constricted extremity.

Reviewed by Dr. Sara Connolly, August 2019

Takeaways

  • ABS is when the inner sac surrounding the baby, or the amnion, ruptures, leaving behind fibrinous strings in the amniotic fluid.
  • No two amniotic band birth defects are the same.
  • Many times, a baby will need surgical reconstruction on the affected body part.

References

  1. Amniotic Band Syndrome. About ABS.
  2. NeoReviews. Amniotic Band Sequence.
  3. Pediatrics in Review. Amniotic bands.

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