What Is Amniotic Constriction Band Syndrome?
Amniotic constriction band syndrome, also known as constriction ring syndrome, occurs when the fibrous lining of the amniotic sac is damaged during pregnancy. This creates string-like strands of tissue in which the developing fetus gets tangled. These strands, called amniotic bands, may rotate around different parts of the developing body, such as the fetus's arm, leg, fingers, or toes. This cuts off the blood supply, keeps the baby from growing normally, and causes a wide range of birth defects. This birth defect can range from mild to severe malformations or life-threatening problems.
What Is the Incidence Rate of Amniotic Constriction Band Syndrome?
Amniotic constriction band syndrome occurs from 1 in 1200 to 1 in 15000 live births and 1 in 70 stillbirths. It can affect both male and female newborns equally. Almost all cases are sporadic and do not appear to be hereditary or genetic.
What Are the Causes of Amniotic Constriction Band Syndrome?
Amniotic constriction band syndrome is not thought to be genetic or hereditary. The exact cause and underlying mechanisms of amniotic constriction band syndrome are unknown, but several theories are proposed to explain the complex mechanisms.
The widely accepted theory is the amnion rupture in early pregnancy, between 28 days after conception and 20 weeks of pregnancy. The fibrous bands of amnion that result from the rupture can tangle around the limbs, resulting in amputations and tourniquet-like defects. This can also occur later in the pregnancy, but this is more commonly seen as the result of amniocentesis (a procedure in which amniotic fluid is removed from the uterus) or fetal surgery.
When amniotic constriction band syndrome occurs later in the pregnancy, it mostly causes no effect on the baby. The complications will be severe when the condition develops during the first 20 weeks of pregnancy.
What Are the Signs and Symptoms of Amniotic Constriction Band Syndrome?
Typically, the earlier the amniotic band syndrome appears, the more severe the complications. It is said that no two cases of amniotic band syndrome are alike, and the effects can vary from one baby to the next. Some infants may develop only mild deformities, while others develop severe and life-threatening malformations. Normally, it is considered that the features of amniotic band syndrome develop in the first 20 weeks of pregnancy.
Mostly, newborns with amniotic band syndrome have deformities with their arms and legs or toes and fingers. In some cases, one or more limbs may be affected. Upper limbs are affected often when compared with lower limbs. In some newborns, only one hand, limb, or foot may be a symptom of this disorder. The specific physical features may include webbing of fingers or toes, abnormally short fingers or toes with the absence of the end portion, tissue adhering to the fingers, and constriction rings. The constriction rings that wrap a limb or digit can alter blood flow. The next pattern associated with amniotic constriction band syndrome is the limb-body wall complex, a life-threatening condition.
In affected infants, it causes protrusion of a portion of the brain and surrounding membranes called meninges through the defect in the skull. It can cause facial clefts in some infants, and protrusion of the soft internal organs, including those found in the chest or abdominal cavities, through a fissure in the abdominal or chest wall. And in a few cases, various defects can be seen affecting the arms and legs.
A third pattern seen associated with amniotic band syndrome is craniofacial abnormalities such as,
-
Facial clefts.
-
Cleft palate (incomplete closure of the roof of the mouth).
-
Microphthalmia (small, underdeveloped eyes).
-
Choanal atresia (narrowing of the nasal passages).
-
Malformations affect the shape and size of the skull.
How Is Amniotic Constriction Band Syndrome Diagnosed?
Amniotic band syndrome is usually diagnosed at or soon after birth based on typical physical findings because the amniotic bands are hard to see on a routine ultrasound. In some cases, if the doctors suspect any abnormalities before birth (prenatally), they may refer the pregnant woman to a fetal center for more advanced testing and care.
Fetal Ultrasonography - During fetal ultrasonography, high-frequency sound waves are used to create the developing fetus image, which may reveal characteristic defects like ring-like constriction and strands of tissue attached to the ends of affected fingers, and a fusion between some digits.
-
Anatomy Ultrasound - This test helps confirm the diagnosis, determine where the bands are located, and evaluate blood flow.
-
Fetal Echocardiogram - This helps to detect the baby's heart structure and function.
-
MRI (Magnetic Resonance Imaging) – It assesses the severity of constriction and abnormalities.
What Are the Treatment Options for Amniotic Constriction Band Syndrome?
Once the amniotic constriction band is diagnosed, the doctors will closely monitor the pregnancy and the baby's growth and development. Regular ultrasounds will help the medical team develop a plan of care by finding changes, risks, and possible problems.
Fetal Surgery - Fetal surgery aims to release the constriction created by the amniotic band before it causes further damage. This is made possible by operative fetoscopy, which allows the visualization of the amniotic band and releasing it using various surgical techniques. The success of this surgery depends on the degree of damage caused by the amniotic band. If the end of the limbs is swollen, releasing the band will aid in resolving the swelling and allow normal development to continue. If the constriction has been severe, then the release of the band can prevent further damage and amputation of the affected limbs.
Physical or Occupational Therapy - Some infants will require rehabilitative therapies to increase their strength and function. The type of physical or occupational therapy depends on the birth defect.
Prosthetics - Infants who have lost a limb may need a prosthesis. It is an artificial device used to replace a missing body part. Advancements in 3-D printing and other technology have vastly improved these devices. They help babies regain limb function as early as 12 to 18.
Conclusion:
Amniotic constriction band syndrome is a rare but severe complication affecting infants. Its exact cause is still unknown. But it can lead to severe deformities in newborns, including amputation. Treatment for amniotic constriction band syndrome depends on the severity of the condition; new advancements in the medical field help regain infants' everyday activities. Adequate prenatal testing will help detect abnormalities at the earliest. Therefore, do not skip prenatal check-ups.
