What is Amniotic Band Sequence and what causes it?
Amnion is a membrane that surrounds the baby in utero. If it ruptures, strands of amnion can end up floating in the amniotic sac. These strands can attach to the baby’s developing body parts and cause injury. This is known as Amniotic Band Sequence (ABS).
Untreated, the bands become tighter around the body part they are attached to, which is why ABS often leads to amputation, severe deformity of limbs, webbed toes or fingers, or severe defects of the head, face, or spine. It is rare, occurring in 1 out of every 1,000 to 2,000 births.
No one knows for certain exactly what causes ABS, but many physicians and researchers agree that it starts with the rupture of the amnion (a thin sac that forms around the fetus that protects it) early in pregnancy. Bands of amnion then encircle parts of the fetus’ body. The rupture of the amnion appears to be random and is not related to anything the mother did or did not do during pregnancy. Further, even if it has occurred in a previous pregnancy, it is unlikely to occur again in another pregnancy.
How is Amniotic Band Sequence diagnosed?
A routine prenatal ultrasound, as early as 12 weeks of gestation, can show the primary effects of the band on the affected extremity. We can then use Doppler blood flow studies to measure how severely the blood flow is restricted. The side effects can range from mild to severe, from swollen limbs to absent limbs or digits.
The SSM Health St. Louis Fetal Care Institute is one of the few fetal surgery centers that can diagnose the severity of the amniotic band, and is one of the few fetal surgery centers that can use fetoscopic surgery to remove the bands in utero, preventing further damage. In severe cases of ABS, fetal surgery may be the best option.
How is Amniotic Band Sequence managed and treated during pregnancy?
We examine each case of ABS closely to confirm that the condition is actually ABS, and not a uterine fold. If we find an amniotic band, our team of doctors and nurses find the best way to prevent progressive injury.
If the amniotic band is touching an area of the baby but not causing injury or cutting off blood flow, no surgery is necessary. If we find that the amniotic band is threatening the baby’s life by impeding blood flow to a limb, entangling the umbilical cord, or threatening to cause a severe deforming or facial problem, fetoscopic surgery may be an option.
During this surgery, the surgeon inserts a pencil-tip-sized scope in the mother’s uterus and uses a laser to cut the amniotic band. This procedure immediately reduces the pressure on the affected extremity and allows it to develop normally, without any further damage.
The staff at the Fetal Care Institute and the team of specialists that works with you is here to support you by arming you with knowledge of all your options, and helping you decide what is right for you and your family.
What happens after surgery?
After surgery, we follow the patient closely throughout the pregnancy to monitor the affected extremity. Fetal surgery does have risks, including preterm labor, infection, and bleeding, but we can treat patients with medications to reduce the risk of these complications.
After a baby with ABS is born, the affected body part will be examined by a plastic surgeon and orthopedic specialist to determine if any additional treatment is needed.