During pregnancy, the amniotic sac surrounds the fetus in the womb and provides it with the extra protection it needs to stay safe while a pregnant woman goes about her normal daily routine. This fluid-filled membrane provides a cushion that lets the fetus continue developing safely while the mother exercises, bends over and picks things up — or even when she bumps into other people or objects.
However, in rare cases, strands of the amniotic sac separate from that inner lining and begin to create a threat for the baby. Amniotic band syndrome, or ABS, occurs when the baby gets entangled in these string-like bands. As the baby continues growing and developing, the bands tighten and can restrict blood flow to certain areas of his or her body. When that happens, it affects how well those body parts develop.
What Are the Effects of Amniotic Band Syndrome?
Exactly how the baby is affected depends upon the severity of the case, but the condition overall is associated with a variety of birth defects. These defects are related to the parts of the body that didn’t receive proper blood flow, and they can range from a single, isolated problem to multiple complications. There are three effects or patterns that are typically seen in babies with ABS, depending on the severity of the case.
The arms and legs are most often affected by ABS. In the least serious cases, a band can wrap around the fingers or toes of the fetus, and according to the National Organization for Rare Disorders, most babies with ABS will have some type of deformity in their arms and legs or fingers and toes. The upper part of the body is more likely to be affected than the lower limbs, and it can affect more than one of their limbs. However, in some cases, the only symptoms might be seen in just one hand or one foot.
Signs of this mildest effect will include fingers or toes that are shorter than normal and are missing the end portion of the digit(s); webbing or fusing of the fingers or toes; or constriction rings around an affected limb or digit, which alters blood flow. There may also be extra strands of tissue attached to the fingers.
A second effect of ABS that may develop is a lethal condition called the limb-body wall complex. In this case, part of the brain and its surrounding membrane might protrude through the skull, or some of the soft internal organs from the chest and abdominal area might protrude from the body.
Finally, the third effect of ABS is craniofacial abnormalities that can include facial clefts or a cleft palate, narrow nasal passages, a malformed skull or small, underdeveloped eyes. This effect can also result in the placenta adhering to the infant’s head.
While ABS creates health complications for the infant, it has not been connected to any risks to the mother’s health during the pregnancy.
What Causes Amniotic Band Syndrome?
ABS is a rather rare condition, with occurrence-rate estimates ranging from one in 1,200 births to one in 15,000. Overall, the cause of the condition is unknown, although damage to the amniotic sac is believed to be a major contributor to developing ABS. In some cases, the amniotic sac might rupture or tear for an unknown reason, but some environmental factors are believed to contribute to it. This can include trauma to the abdominal area during pregnancy or blunt trauma to the placenta.
For reasons that still aren’t entirely clear, ABS occurs more often in first pregnancies and in problem pregnancies or those involving premature births. There’s also a higher rate of it occurring among young women and women of African descent, although research is still trying to determine why it’s more common among some populations than others.
How Is Amniotic Band Syndrome Diagnosed and Treated?
Although ABS is often not detected until the baby is born, it can be diagnosed earlier through advanced ultrasound techniques. Such ultrasound tests can detect the bands as they begin to appear, and while mild cases may only require monitoring as the baby grows, more severe cases could require surgical intervention.
In utero surgery can free the baby’s limbs from amniotic bands that could prevent them from growing or that could threaten to amputate the limbs. Performing a minimally invasive fetoscopy allows the fetal surgeon to insert a fetoscope that is able to cut the bands around the baby’s limbs, fingers or toes and allow the blood flow to resume properly.
If ABS is not detected until after the baby is born, reconstructive surgery can help correct or repair malformations that have occurred in the womb. This includes operating on webbed fingers and toes and correcting problems like a cleft lip or club foot. Children who have lost limbs or don’t have complete functionality in their limbs might be fitted with prosthetic devices.
What Is the Outcome for Amniotic Band Syndrome?
The long-term diagnosis for a baby born with ABS will depend on the severity of the condition. Babies who are only affected in their limbs have shown excellent outcomes, even if amputation was required. Babies with problems such as a cleft lip and cleft palate now have surgical options that weren’t previously available, so they now have a better prognosis. However, despite the many advancements that have been made in pediatric surgery, some babies may still have some type of disfigurement.
For babies whose internal organs have been exposed, there may not be options for long-term survival.
How Can I Prevent Amniotic Band Syndrome?
Because the cause of ABS is damage to the amniotic sac, most experts consider ABS to be a random event. The odds of it happening in another pregnancy with the same mother is highly unlikely, and it is not considered to be a genetic disorder.
While there is no known way to prevent it from occurring, early fetal diagnostic testing allows for monitoring of the condition and, if needed, fetal surgery to correct problems that could cause long-term damage to the baby.
The Fetal Care Center in Dallas is one of only a few centers worldwide with the capability to perform the full range of fetal interventions. If you have a question or wish to make an appointment, please call 972-566-5600 for urgent or same-day appointments. We are here for you and your family.