Amniotic band syndrome or ABS occurs due to a pregnancy complication in which the fetus gets entangled with string-like amniotic bands. It hampers the growth and development of the baby by restricting the blood supply to certain body parts. ABS often leads to physical disabilities as well as congenital deformities – facial (eye, nose), head, arm, finger, foot and toe . 
Other Names: Amniotic band constriction, congenital constriction bands, amniotic band sequence,  ADAM (amniotic deformity, adhesions, mutilations) complex, pseudoainhum, amnion rupture sequence, constriction band syndrome and streeter anomaly.
Depending on the degree of amniotic band constriction, the signs and symptoms may vary from cosmetic defects to more serious deformities. 
Other associated congenital defects include clubfoot, radial club hand (radial dysplasia), hemangioma, syndactyly, neural tube defects (anencephaly and myelomeningocele) and limb-body-wall complex. The fibrous strings may even cause fetal death and miscarriage by constricting the umbilical cord, cutting off the nutrient and oxygen supply to the fetus. 
The exact reasons responsible for the abnormal condition is still unknown to researchers. Studies and researches are being carried out to determine factors responsible (genetic, hereditary, or both) and their role. Among the several proposed theories, the extrinsic and the intrinsic ones are most widely considered.
The extrinsic theory shows ABS to be resulting from factors outside the fetus.  According to researchers, sometimes the inside membrane (amnion) of the amniotic sac surrounding the baby in the uterus gets ruptured, causing thin fibrous strands of tissue (amniotic constriction bands) to float around in the amniotic fluid. The outer membrane or chorion remains intact, making it difficult to detect the rupture. The floating amniotic bands often get encircled around the limbs or other body parts of the developing fetus. Eventually as the fetus grows, the bands start constricting the blood supply in the entangled areas, hindering their development. This leads to physical malformations and other birth defects in the affected babies.
Although the above theory explains most cases of ABS, it remains insufficient for explaining the high incidence of internal organ defects (like cleft palates) and the presence of an intact amniotic sac in some cases . The intrinsic theory suggests inadequate blood circulation to certain parts of the fetus leads to development of amniotic band syndrome, thus causing deformities.
There is no known way to prevent ABS due to its unknown etiology. However, avoiding the possible risk factors may reduce the chances of having a baby with such birth defects.
The doctor performs a physical examination of the newborn baby to diagnose this abnormality. Imaging tests like x-ray and MRI may be required to determine the extent of damage . MRI scans also help with the detection of any nervous or vascular damage.
Prenatal diagnosis is difficult as the amniotic bands often remain undetectable on fetal ultrasound. But in some cases, doctors can detect ABS indirectly, based on any abnormal swelling of hands and feet of the baby visible on ultrasound images. In such cases, the constriction bands can be observed as early as the first trimester (12th week) . Additional screening tests may be necessary for confirming the diagnosis as misdiagnosis of ABS is quite common due to its idiopathic nature. Fetal echocardiogram exams are usually recommended for assessing the baby’s heartbeat and to rule out associated heart defects. 
The treatment depends on the time of diagnosis and severity of the damage . Mild cases may not require any treatment while children suffering from severe ABS often need lifelong medical care. Women carrying babies with severe amniotic band constriction are sometimes brought to special medical centers before delivery so that medical specialists can take care of the complications as soon as the baby is born.
Fetal surgery carries significant risk of fetal death resulting from premature delivery. Other possible complications include bleeding and infection of both the mother and baby .
Statistics show its incidence to be around 1 in every 1,200 live births while its frequency in miscarriages is approximately 178 in 10,000 cases. 
The outcome of treatment in each case is different, based on the nature and location of the damage as well as the undertaken treatment procedure. The risk of recurrence in a following pregnancy is extremely low . Patients suffering from mild ABS can lead relatively normal lives and reach adulthood.
Its ICD-9 code is 762.8 while the IDC-10 code is P02.8.
Birth Defect Research for Children, Inc.
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