Introduction
Amniotic (annular) band syndrome is a rare condition caused by the strands of the amniotic sac that entangle the limbs, digits, or other parts of the fetus, resulting in a variety of problems depending on the location of the strand and how tightly it is wrapped.
What Is Amniotic Band Syndrome (ABS)?
In the mother’s uterus, the developing fetus floats in the amniotic fluid. The amniotic sac keeps the fluid around the fetus inside the uterus. This sac is made of two layers that are stuck together. The outer layer is called the chorion, and it lines the uterus, whereas the inner layer is called the amnion that lies close to the fetus.
It is said that amniotic band syndrome or constriction ring syndrome occurs when there is a rupture or tear in the inner lining (amnion) of the sac without any injury to the outer lining (chorion). The developing fetus, which is still floating in the amniotic fluid, gets exposed to the floating tissues (by the rupture of amnion), which are named bands. These floating tissues become entangled around the fetus, leading to the constriction (tightening) of digits, limbs, or other body parts of the fetus.
In rare cases, the band entangles the fetus's head or the umbilical cord. These bands act like rubber bands that affect the fetus on more than one part of the body. The incidence is very rare and occurs in one in 1200 to one in 15,000 live births. However, the cause is not known.
What Factors Increase the Risk of Amniotic Band Syndrome?
Being more likely to have ABS can occur if certain factors are present, which include
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Experiencing complications throughout the pregnancy.
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Possessing vascular Ehlers-Danlos syndrome.
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Smoking during pregnancy.
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Engaging in the use of illegal drugs or consuming specific medications during pregnancy.
What Are the Symptoms of Amniotic Band Syndrome?
The amniotic band might cause a small dent around the digit or the limb. Deeper bands can cause serious swellings, cut off the blood flow, or disrupt the body's growth. If the band is too tight, it may cause an in-utero amputation. Some of the features are common in amniotic band syndrome. They are:
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Distal ring constriction.
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Limb deformity.
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Intrauterine amputation.
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Webbed fingers and toes.
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Progressive lymphedema.
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Clubfoot or club hands.
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Stunted growth of fingers and toes.
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Limb length discrepancy.
Less common features are:
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Pseudoarthrosis.
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Metatarsus adductus.
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Peripheral nerve palsy.
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Dystrophic nails, etc.
Finally, fetal death associated with amniotic band strangulation has also been reported.
What Causes Amniotic Band Syndrome?
Amniotic band syndrome is caused by the entrapment of fetal parts (limbs or digits) in the fibrous band in utero. It is not a genetic or hereditary disease, and the exact cause is not known. Many cases happen for no obvious reason. It is, therefore, unlikely that the amniotic band syndrome will affect a fetus in a future pregnancy. The commonly accepted theory is that when the inner membrane called the amnion ruptures without any injury to the chorion, it leads to amniotic band syndrome. This injury or rupture exposes the baby to fibrous sticky bands of the placenta that float in the amniotic fluid. These bands then entangle the fetus's body parts and lead to some deformities.
How Serious Is the Fetus Amniotic Band Syndrome?
Each case of amniotic band syndrome is different. The severity of the syndrome is identified by the number of bands that may be entangled around the fetus or by how tightly they are wounded. When amniotic bands are evident, a detailed ultrasound is performed to assess the severity of the syndrome.
Amniotic bands are difficult to detect through ultrasound because of their small size; thus, it is important to be reviewed by someone who has deep knowledge of amniotic band syndrome. The individual strands are hard to see; thus, the condition is detected indirectly by the swelling or constriction of the limbs or other body parts.
What Can Be Done After Birth?
A fetus with this syndrome might require treatment after birth. Possible treatment modalities include reconstructive surgery to correct deep grooves, fused fingers, cleft lips, or clubbed feet.
Does This Syndrome Affect Pregnancy?
This syndrome imposes no risk for the mother during pregnancy. Most complications are handled post-birth. For severe cases, a detailed examination is necessary to undergo fetal surgery. Fetal surgery is suggested when the band is around the limb and causes restricted blood flow to the limb. In mild situations, fetal surgery is not suggested, and the complications are treated after birth by reconstructive surgery.
What Are the Other Conditions Associated With Amniotic Band Syndrome?
Some children with this condition may have:
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Cleft lip.
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Cleft palate.
How Is Amniotic Band Syndrome Diagnosed?
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Amniotic band syndrome is diagnosed through ultrasound examination before birth.
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Most of the time, this condition is diagnosed when the baby is born.
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X-ray examination helps in diagnosing the severity of the condition.
How Is Amniotic Band Syndrome Treated?
Treatment of this condition varies depending on the child and the severity. Treatment is symptomatic.
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If the bands are shallow, they do not interfere with the functioning of the body and, hence, do not require treatment.
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If the bands are deeper, one or more surgeries are needed to fix the defect.
Surgery is usually done when the child crosses one year of age. Immediate surgery is planned when the band is limiting the blood flow. In utero, surgeries are performed when the amputation seems to be imminent.
What Is the Prognosis for Individuals With Amniotic Band Syndrome?
Babies with mild ABS generally have a positive prognosis. Kids born with limb conditions generally adjust effectively to rehabilitation and prosthetics. Infants experiencing severe lung, brain, or other dysfunction often do not make it through.
Conclusion
The amniotic band syndrome, also known as annular band syndrome, occurs when the bands from the inner layer (amnion) compress the soft tissue involving the deep fascia at the time of birth (in utero). This condition occurs sporadically, and the incidences are rare. The etiology is usually not known. However, it is considered to be caused by the strands of the amniotic sac that entangle the limbs, digits, or other parts of the fetus, resulting in a variety of problems depending on the location of the strand and how tightly it is wrapped. Treatment is symptomatic and depends upon the obstruction caused by the band. Since the condition is not linked to heredity or genes, future pregnancies are not affected by it.
