Amniotic band syndrome
Encyclopedia
Amniotic band syndrome is a congenital disorder
caused by entrapment of fetal parts (usually a limb or digits) in fibrous amniotic bands while in utero.
s. Up to 50% of cases have other congenital anomalies including cleft lip, cleft palate, and clubfoot deformity. Hand and finger anomalies occur in up to 80%.
A strong relationship between ABS and clubfoot exists. A 31.5% of associated clubfoot deformity and ABS can be correlated with 20% occurring bilaterally. Other abnormalities found with ABS include: clubhands, cleft lip, and/or cleft palate, and hemangioma
.
The amniotic band theory is that ABS occurs due to a partial rupture of the amniotic sac
. This rupture involves only the amnion
; the chorion
remains intact. Fibrous bands of the ruptured amnion float in the amniotic fluid
and can encircle and trap some part of the fetus. Later, as the fetus grows but the bands do not, the bands become constricting. This constriction reduces blood circulation, hence causes congenital abnormalities. In some cases a complete "natural" amputation
of a digit(s) or limb may occur before birth or the digit(s) or limbs may be necrotic (dead) and require surgical amputation following birth.
The vascular disruption theory:
Because the constricting mechanism of the amniotic band theory does not explain the high incidence of cleft palate and other forms of cleft defects occurring together with ABS, this co-occurrence suggests an "intrinsic" defect of the blood circulation.
In rare cases, if diagnosed in utero, fetal surgery
may be considered to save a limb which is in danger of amputation or other deformity. This typically would not be attempted if neither vital organs nor the umbilical cord
are affected. This operation has been able to be successfully performed on fetuses as young as 22 weeks. The surgery took place at Melbourne's Monash Medical Centre in Australia
and is believed to be the earliest surgery of its type, as surgeons usually hold off on operating until a mother is at least 28 weeks gestation. There are also several facilities in the United States that have performed successful amniotic band release surgery.
depends on the location and severity of the constricting bands. Every case is different and multiple bands may be entangled around the fetus.
Bands which wrap around fingers and toes can result in syndactyly
or amputation
s of the digits. In other instances, bands can wrap around limbs causing restriction of movement resulting in clubbed feet. In more severe cases, the bands can constrict the limb causing decreased blood supply and amputation. Amniotic bands can also sometimes attach to the face or neck causing deformities such as cleft lip and palate. If the bands become wrapped around the head or umbilical cord it can be life threatening for the fetus.
The number of cases of miscarriage
that can be contributed to ABS is unknown, although it has been reported that it may be the cause of 178 in 10,000 miscarriages.
Congenital disorder
A congenital disorder, or congenital disease, is a condition existing at birth and often before birth, or that develops during the first month of life , regardless of causation...
caused by entrapment of fetal parts (usually a limb or digits) in fibrous amniotic bands while in utero.
Epidemiology
Amniotic banding affects approximately 1 in 1,200 live births. It is also believed to be the cause of 178 in 10,000 miscarriageMiscarriage
Miscarriage or spontaneous abortion is the spontaneous end of a pregnancy at a stage where the embryo or fetus is incapable of surviving independently, generally defined in humans at prior to 20 weeks of gestation...
s. Up to 50% of cases have other congenital anomalies including cleft lip, cleft palate, and clubfoot deformity. Hand and finger anomalies occur in up to 80%.
Features
The constriction of appendages by amniotic bands may result in:- Constriction rings around the digits, arms and legs
- Swelling of the extremities distal to the point of constriction (congenital lymphedemaCongenital lymphedemaCongenital lymphedema is a blockage of fluid in the developing fetal lymphatic system. It is diagnosed by a nuchal scan. Presence of this condition is also associated with congenital heart defect....
) - Amputation of digits, arms and legs (congenital amputationCongenital amputationCongenital amputation is a congenital disorder that can be caused by fibrous bands of the amnion that constrict foetal limbs to such an extent that they fall off due to missing blood supply. The child is born without one or more limbs or without parts of limbs .-Causes:Congenital amputations can...
)
A strong relationship between ABS and clubfoot exists. A 31.5% of associated clubfoot deformity and ABS can be correlated with 20% occurring bilaterally. Other abnormalities found with ABS include: clubhands, cleft lip, and/or cleft palate, and hemangioma
Hemangioma
A hemangioma of infancy is a benign self-involuting tumor of endothelial cells, the cells that line blood vessels. It usually appears during the first weeks of life and sometimes resolves by age 10. In more severe case hemangioma may have permanency, if not treated by a physician...
.
Natural history
To explain the cause of ABS, there are two main theories.The amniotic band theory is that ABS occurs due to a partial rupture of the amniotic sac
Amniotic sac
The amniotic sac is the sac in which the fetus develops in amniotes. It is a tough but thin transparent pair of membranes, which hold a developing embryo until shortly before birth. The inner membrane, the amnion, contains the amniotic fluid and the fetus. The outer membrane, the Chorion,...
. This rupture involves only the amnion
Amnion
The amnion is a membrane building the amniotic sac that surrounds and protects an embryo. It is developed in reptiles, birds, and mammals, which are hence called “Amniota”; but not in amphibians and fish , which are consequently termed “Anamniota”. The primary role of this is the protection of the...
; the chorion
Chorion
The chorion is one of the membranes that exist during pregnancy between the developing fetus and mother. It is formed by extraembryonic mesoderm and the two layers of trophoblast and surrounds the embryo and other membranes...
remains intact. Fibrous bands of the ruptured amnion float in the amniotic fluid
Amniotic fluid
Amniotic fluid or liquor amnii is the nourishing and protecting liquid contained by the amniotic sac of a pregnant woman.- Development of amniotic fluid :...
and can encircle and trap some part of the fetus. Later, as the fetus grows but the bands do not, the bands become constricting. This constriction reduces blood circulation, hence causes congenital abnormalities. In some cases a complete "natural" amputation
Congenital amputation
Congenital amputation is a congenital disorder that can be caused by fibrous bands of the amnion that constrict foetal limbs to such an extent that they fall off due to missing blood supply. The child is born without one or more limbs or without parts of limbs .-Causes:Congenital amputations can...
of a digit(s) or limb may occur before birth or the digit(s) or limbs may be necrotic (dead) and require surgical amputation following birth.
The vascular disruption theory:
Because the constricting mechanism of the amniotic band theory does not explain the high incidence of cleft palate and other forms of cleft defects occurring together with ABS, this co-occurrence suggests an "intrinsic" defect of the blood circulation.
Diagnosis
Amniotic band syndrome is often difficult to detect before birth as the individual strands are small and hard to see on ultrasound. Often the bands are detected indirectly because of the constrictions and swelling upon limbs, digits, etc. Misdiagnosis is also common, so if there are any signs of amniotic bands, further detailed ultrasound tests should be done to assess the severity. 3D ultrasound and MRI can be used for more detailed and accurate diagnosis of bands and the resulting damage/danger to the fetus.Treatment
Treatment usually occurs after birth and where plastic and reconstructive surgery is considered to treat the resulting deformity. Plastic surgery ranges from simple to complex depending on the extent of the deformity. Physical and occupational therapy may be needed long term.In rare cases, if diagnosed in utero, fetal surgery
Fetal surgery
Fetal surgery is any of a broad range of surgical techniques that are used to treat birth defects in fetuses who are still in the pregnant uterus.* Open fetal surgery involves completely opening the uterus to operate on the fetus....
may be considered to save a limb which is in danger of amputation or other deformity. This typically would not be attempted if neither vital organs nor the umbilical cord
Umbilical cord
In placental mammals, the umbilical cord is the connecting cord from the developing embryo or fetus to the placenta...
are affected. This operation has been able to be successfully performed on fetuses as young as 22 weeks. The surgery took place at Melbourne's Monash Medical Centre in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and is believed to be the earliest surgery of its type, as surgeons usually hold off on operating until a mother is at least 28 weeks gestation. There are also several facilities in the United States that have performed successful amniotic band release surgery.
Prognosis
The prognosisPrognosis
Prognosis is a medical term to describe the likely outcome of an illness.When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because...
depends on the location and severity of the constricting bands. Every case is different and multiple bands may be entangled around the fetus.
Bands which wrap around fingers and toes can result in syndactyly
Syndactyly
Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, such as the siamang and kangaroo, but is an unusual condition in humans.-Classification:...
or amputation
Congenital amputation
Congenital amputation is a congenital disorder that can be caused by fibrous bands of the amnion that constrict foetal limbs to such an extent that they fall off due to missing blood supply. The child is born without one or more limbs or without parts of limbs .-Causes:Congenital amputations can...
s of the digits. In other instances, bands can wrap around limbs causing restriction of movement resulting in clubbed feet. In more severe cases, the bands can constrict the limb causing decreased blood supply and amputation. Amniotic bands can also sometimes attach to the face or neck causing deformities such as cleft lip and palate. If the bands become wrapped around the head or umbilical cord it can be life threatening for the fetus.
The number of cases of miscarriage
Miscarriage
Miscarriage or spontaneous abortion is the spontaneous end of a pregnancy at a stage where the embryo or fetus is incapable of surviving independently, generally defined in humans at prior to 20 weeks of gestation...
that can be contributed to ABS is unknown, although it has been reported that it may be the cause of 178 in 10,000 miscarriages.
Prevention
Amniotic band syndrome is considered an accidental event and it does not appear to be genetic or hereditary, so the likelihood of it occurring in another pregnancy is remote. The cause of amnion tearing is unknown and as such there are no known preventative measures.External links
- amnioticbandsyndrome.com - Information, Photos, Personal Stories of ABS, Online Community
- UCSF Fetal Treatment Center: Amniotic Band Syndrome
- SuperHands Kids and Heroes Support Group for parents of kids with upper limb differences
- Cincinnati Children's Hospital Fetal Care Center resources- one of the locations that has performed amniotic band release surgery
- Support and information for families dealing with fetal syndromes such as amniotic band syndrome
- Monica - a case study of a young woman born with amniotic band syndrome