Children's Hospital Colorado

Amniotic Band Syndrome

Amniotic band syndrome (ABS) is a group of randomly occurring abnormalities that involve any part of the developing baby: arms and legs being more common, but also the head, face, chest or abdomen. The amnion is one of the two layers that form the amniotic sac, commonly referred to by patients as “the water bag.” If the amnion tears or is damaged, then bands may potentially form, called amniotic bands. The disruption in the amnion can occur anytime between 6 and 18 weeks of pregnancy. The earlier the bands form, the more likely it is for these bands to result in serious, life-altering consequences.

Amniotic Band Medical Illustration

Current studies estimate that ABS can happen in 1 out of every 1200 live births. The bands that form can attach and tighten (constrict) around any developing structure including the umbilical cord, which is the lifeline between mother and baby. The bands might also tear normally developing structures causing the structures to then abnormally develop or even be cut off (amputated), such as fingers, toes, hands and feet. The bands can even cause the spine to curve abnormally in any direction. If a band is visualized, it does not automatically mean that your baby has suffered damage. Sometimes, it might be difficult to visualize the amniotic bands by ultrasound. There may be a role for fetal surgery (operating on the baby while still inside the uterus) in ABS if the bands involve tightening of the umbilical cord, a life-threatening condition.  Fetal surgery may also be recommended if there is a threatened limb amputation from a very tight band. A fetus with ABS should pose no increased risk for the mother in the management of the pregnancy. There is no indication for cesarean section simply based on the diagnosis of ABS. The outcome in ABS depends on the structure involved. There is no increased risk of this condition happening again in a future pregnancy.

For Patients

Amniotic band syndrome, or ABS, refers to conditions caused by damage to the amnion, the sac surrounding the fetus in utero. When this sac is partially disruptured, fibrous strings, or bands, can enter the amniotic fluid and wrap around parts of the baby’s body, hindering growth. Most cases involve bands that wrap around the arms, legs or digits, with more rare cases involving the head or trunk.  

Learning that your baby could develop abnormalities due to amniotic band constriction can be terrifying. But the Colorado Fetal Care Center (CFCC) is a national leader in diagnosing and treating the condition. Read more about the talented fetal care specialist and why they’re uniquely capable of helping your family.

The symptoms of ABS vary depending on when the damage to the amniotic sac occurs, as well as which of the baby’s body parts are constricted by the amniotic bands.  Possible symptoms include limb deformities such as clubfoot, stunted growth of fingers and toes, webbed toes or fingers, and cleft palate. In the most severe cases, amniotic bands cause organ damage or miscarriage (by severing the umbilical cord).

The good news is that early diagnosis and in utero surgery at specialist clinics such as the Colorado Fetal Care Center can potentially save a baby’s life or limbs if at risk. In cases that do not threaten life or a limb, postnatal surgery might minimize or reverse the effects of birth defects once a baby is born. 

The Colorado Fetal Care Center (CFCC) tailors treatment of amniotic band syndrome to your child's specific needs. Amniotic band syndrome is usually treated after birth through surgery.

Amniotic Band Syndrome Treatment Options 

There are multiple amniotic band syndrome treatment options to help your child grow and thrive, both during your pregnancy and after his or her birth.

The Colorado Fetal Care Center is one of the nation’s top care centers for babies facing the effects of amniotic band syndrome, and we have successfully performed surgeries on babies ranging from 16 to 27 weeks gestation.

Once ABS is diagnosed, either by ultrasound during pregnancy or examination after birth, there is a range of amniotic band syndrome treatment options to correct the damage.

TREATMENT OPTION: Fetoscopic Surgery

When an amniotic band is endangering the baby’s life by constricting growth of critical internal organs or threatening the umbilical cord, specialized surgeons perform an in utero procedure to free the baby from the bands. Additionally, while losing a limb in utero due to band constriction is not fatal, prenatal surgery to save the limb is still an option for certain expectant mothers.

TREATMENT OPTION: Surgery after Birth

When babies are born with birth defects caused by band constriction, surgeons can perform a wide range of surgeries to correct or minimize those defects. Examples include reconstructive surgeries to repair cleft palates or cleft lips, as well as others to correct webbed feet or fingers, or reconstruction procedures to correct effects of constrictive bands. 

If your baby is diagnosed with amniotic band syndrome, you probably have many questions. The Colorado Fetal Care Center can help answer them.

What causes amniotic band syndrome?

ABS is caused by fibrous strands, or bands, entering the uterus and wrapping around parts of a baby’s body. As the baby grows, the bands tighten and constrict growth and blood flow. The bands usually enter the uterus due to a partial rupture of amnion, the sac surrounding the baby.

What is an amniotic band?

When the amnion ruptures, fibrous strands of tissue that were part of it float in the waters of the uterus. These are amniotic bands, and they can wrap around the baby’s body parts and cause deformities.

What is the long-term outcome for babies with amniotic band syndrome?

The outcome depends on many variables: The timing of the amnion’s rupture during the pregnancy and the location of the band constriction, whether and how accurately the condition is diagnosed (usually through an ultrasound or at birth) and the severity of the damage from band constriction. By definition, all cases of amniotic band syndrome have PPOROM (Preterm Premature Rupture of membranes) and the average gestational age delivery is 32 weeks. Your physicians will address the details of your situation and create a treatment approach designed to maximize your baby’s lifelong health.

Will I need to have a c-section?

There is no indication for cesarean section simply based on the diagnosis of amniotic band syndrome or even after fetoscopic surgery.

Will this happen in future pregnancies?

There is no increased risk of this condition happening again in a future pregnancy.

For Healthcare Professionals

Amniotic Band Syndrome is associated with numerous antenatal sonographic features, as there are numerous forms of the syndrome and these features may occur as isolated problems or in combination. The earliest that amniotic bands have been seen is at 12 weeks of gestation, by an endovaginal probe. The bands can be extremely difficult to detect sonographically and amniotic band syndrome is more often diagnosed by the effect that they have on fetal anatomy. The effect of amniotic bands on the extremities may be manifested by absent digits or portions of limbs, or a swollen distal arm or leg resulting from constrictive amniotic bands (Paladini et al. 2004). ABS may affect the face with cleft lip or palate, asymmetric microphthalmia, or severe nasal deformity. Encephalocele may be a manifestation of ABS, especially when eccentrically placed.

Abdominal-wall defects can be the result of ABS, typically with large defects with free-floating intestine herniated outside the abdomen. The characteristic appearance of an aberrant sheet or band of amnion attached to the fetus with resultant deformity and restriction of motion allows a diagnosis of ABS to be made. However, prenatal diagnosis is the exception rather than the rule.

Sonographic image of a 20 week fetus with a constricting amniotic band of the upper extremity.

Sonographic image of a 20-week fetus with a constricting amniotic band of the upper extremity.

The findings in ABS may be limited to isolated defects, including isolated facial cleft, digital amputation, or mild elephantiasis of an extremity beyond a constrictive band (Sentilhes et al. 2004, Dyson et al. 2000). These isolated features may be difficult to diagnose sonographically because the detailed fetal visualization required is beyond the scope of routine obstetrical ultrasound examinations. At the worst end of the spectrum, the fetus may be so severely deformed by the amniotic bands that the spine is contracted and organs are formed in perplexing and bizarre proportions. The head may be completely misshapen or absent. The bands responsible for these deformities are rarely seen and a presumptive diagnosis of ABS is made based on the commonly associated deformities.

A 3-D image of a fetus showing a constricting amniotic band of the upper extremity.

A 3-D image of the same fetus showing a constricting amniotic band of the upper extremity.

The spinal deformities in ABS can be severe, manifesting as kyphotic lordosis or scoliosis as well as severe rotational abnormalities and even spinal amputation (Chen 2001). While spinal deformity can be seen in other syndromes, severe spinal deformity should suggest ABS.

Spinal deformity associated with an abdominal-wall defect is particularly suggestive of ABS. While the typical appearance of an omphalocele is possible, the more common defect is a large slash-like defect of both the thoracic and abdominal cavities with evisceration. These defects are associated with exteriorized bowel, liver, and sometimes heart without an enveloping membrane. When associated with limb abnormalities this is characteristic of the limb–body-wall complex form of ABS.

Sonographic image demonstrating an amniotic band floating in amniotic fluid.

Sonographic image demonstrating an amniotic band floating in amniotic fluid.

Deformation of the calvarium is another group of anomalies characteristic of ABS. If complete, the fetus may appear anencephalic or to have acrania (Chen et al. 2004). If partial, the fetus may appear to have an encephalocele. The distinguishing features that characterize these defects as ABS are their asymmetric nature and associated spinal deformity or abdominal-wall defects. In classic anencephaly, the calvarial bones are symmetrically absent. In anencephaly caused by ABS, there is some portion of calvarium present, usually near the base of the skull or near one other orbit. Similarly, classic encephaloceles occur near the midline, while ABS causes encephaloceles off the midline.

The presence of bands is unnecessary for the diagnosis of ABS in the presence of characteristic fetal anomalies. The sonographic detection of bands is helpful in confirming the diagnosis of ABS as the cause of fetal deformity. However, observation of these bands without fetal abnormality is not ABS. It is important for the sonographer to distinguish amniotic bands from other membranes and separations within the amnion. Separation of amnion and chorion is normal in early pregnancy until fusion occurs at approximately 16 weeks of gestation (Burrows et al. 1982; Patten et al. 1986; Sauerbrei et al. 1980).

Chorioamniotic separation may occur as a result of amniocentesis or fetal surgery, and extra chorionic hemorrhage may separate the chorioamniotic membrane from the uterine wall (Burrows et al. 1982; Graf et al. 1997; Spirit et al. 1979). In both of these instances, a membrane may be observed sonographically. Other causes of membranes in the developing fetus include the septate uterus, blighted twin, and circumvallate placenta (Filly et al. 1991).

Adhesions that form in the uterus as a result of curettage, cesarean section, or myomectomy may cause sheets of amnion that protrude into the lumen of the amniotic cavity (Asherman 1948; Comninos et al. 1969; Filly et al. 1991; Mahony et al. 1985; Randal et al. 1988). Randal et al. (1988) found that 76% of patients with amniotic sheets had undergone prior instrumentation. This results in an adhesion that becomes covered by chorion and amnion and has a thickness similar to the intertwin membrane of dichorionic diamniotic twins. These amniotic sheets do not adhere to the fetus because the amnion is intact (Tan et al. 2005). The uterine adhesion may rupture with the growth of the fetus. Filly et al. (1991) have described the sonographic appearance of these synechiae as having a thickened base and a fine edge that undulates. There may be a bulbous edge, presumably due to the synechiae. There are no associated fetal abnormalities and there is free fetal movement around the sheet. The synechiae may not be seen in the third trimester, whether due to rupture or compression by the growing fetus.

In the limb–body-wall complex there is a constellation of abnormalities, including myelomeningoceles or caudal regression, thoraco-abdominoschisis, or abdominoschisis and limb defects. At least two of the three abnormalities listed above are necessary to make a diagnosis of LBWC. The umbilical cord is usually short or absent, with the placenta attached to the fetus. If present, there may be only a two-vessel cord. The limbs may be missing or the feet clubbed. The spine is often short and curved and sacral regression is common. There may be Arnold–Chiari malformation and hydrocephalus associated with the meningomyelocele. There may be ectopia cordis as part of the thoraco-abdominoschisis. Facial clefts may also be seen in LBWC.

ABS involving the umbilical cord can be recognized by abnormal clustering of loops of the umbilical cord which may be adherent to a bend fixed to a limb. These findings may be subtle and should be sought in any case of ABS as umbilical cord involvement may result in fetal demise.

There is great controversy about the pathogenesis of the various forms of Amniotic Band Syndrome. Part of this controversy involves the timing in gestation of the development of amniotic bands. However, in constrictive amniotic bands of the extremities, the progression of constriction combined with fetal growth has resulted in extremity amputation (Hill et al. 1988). ABS can be associated with either polyhydramnios or oligohydramnios. Despite the severity of some forms of ABS, there are no adverse maternal consequences for this diagnosis. The incidence of intrauterine fetal death from ABS involving the umbilical cord is not known but numerous cases have been reported (Graf et al. 1997; Kanayama et al. 1995; Torpin 1965). However, the poorly characterized pathogenesis of this syndrome and limited sonographic surveillance limit our understanding of its prenatal natural history.

ABS is a relatively common if underappreciated, cause of fetal and neonatal morbidity and mortality. The fetal-lamb model of ABS will be useful to better define the pathophysiology of ABS and to provide a tool to understand the unique fetal response to tissue injury, repair, and regeneration. Sonographic identification of ABS affecting the umbilical cord may be an indication for fetoscopic surgical intervention. In the future, intervention for nonlethal limb deformation may also be considered if maternal risk is sufficiently lowered. ABS is another in a growing list of conditions for which fetal surgery may be considered in the future.

Constrictive bands most commonly affect the extremities, but can also involve the umbilical cord, with resulting fetal death. Kanayama et al. (1995) described the reversal of diastolic flow observed in a fetus with umbilical-cord constriction due to amniotic bands. Graf et al. (1997) similarly reported a case of amniotic bands involving the umbilical cord following the development of chorioamniotic separation. Despite initially normal umbilical artery Doppler waveforms, this fetus died within 2 weeks from a constrictive amniotic band of the umbilical cord. Reports have described constrictive amniotic bands as a cause of fetal death (Moerman et al. 1992; Torpin 1965). However, until the reports by Kanayama and Graf and their colleagues, this was a diagnosis made pathologically after the fact. It is in cases like these that fetoscopic lysis of amniotic bands could be lifesaving (see Fetal Intervention).

Cases of ABS, by definition, have ruptured membranes and typically deliver prematurely with an average gestational age of 32 weeks’ gestation.

Several theories have been advanced to explain the occurrence of these anomalies, but two are most commonly held. In 1930 Streeter proposed that a disruption in embryogenesis at the time of formation of the germ disk and the amniotic cavity initiated a chain of events leading to the multiple defects. He suggested that amniotic bands were the result, not the cause, of the pathologic process. In 1992 Bamforth reviewed this theory in a series of 54 cases of ABS and concluded that it may be caused by a localized disturbance in establishment of basic embryonic organization. The most widely accepted theory was proposed by Torpin in 1965. He examined the placenta and fetal membranes in a number of affected individuals and concluded that the disorder was caused by primary rupture of the amnion early in gestation (Herva et al. 1984; Higginbottom et al. 1979; Keller et al. 1978; Seeds et al. 1982).

More recently, Moerman et al. (1992) proposed that the ABS is a collection of three distinct entities that can reconcile the adherents of Streeter’s and Torpin’s hypotheses. They suggested that ABS consists of three distinct lesions: (1) constrictive tissue bands; (2) amniotic adhesions; and (3) the more complex pattern of anomalies designated the limb–body-wall complex (LBWC). In this report of the fetopathologic evaluation of 18 cases of ABS, 4 had clearly constrictive bands, which formed as a result of the amnion rupture sequence. The bands that resulted from amnion rupture encircled the limbs, resulting in annular constrictions, secondary syndactyly, and intrauterine amputations. In addition, constriction of the umbilical cord is a recognized cause of fetal death (Hong et al. 1963; Torpin 1965). These authors distinguish cases caused by constrictive bands from those caused by broad amniotic adhesions. Moerman et al. suggested that adhesive amniotic bands were morphologically and pathogenetically different from constrictive bands. Adhesive amniotic bands are usually associated with severe defects such as encephalocele and facial clefts. This group demonstrated pathologically that cranioplacental adhesions are broad adhesions, with the fetal skin fused to the amnion at the margins of the cranial defect. They speculated that the amnion covering the placenta or membranes seals the cranial defect separating the protruding brain from the chorion. Van Allen et al. (1987) proposed that the amnion becomes adherent to the embryo in areas of ischemic necrosis following vascular disruption. In short, the amniotic adhesions are secondary to fetal defects.

Moerman et al. (1992) considered the LBWC to be due to both band-related and non–band-related defects. The band-related defects include limb defects such as club foot. Non–band-related defects occur as a result of vascular disruptions or from compression (Miller et al. 1981). The thoraco-abdominoschisis of LBWC is characterized by an anterolateral body-wall defect with evisceration of abdominal and/or thoracic organs. The eviscerated organs are in an extraamniotic sac bounded by the chorionic plate, a persistent extraembryonic coelom. The amnion is continuous with the skin. The umbilical cord is extremely short, with umbilical vessels running in the amniotic sac, often with an absent umbilical artery. The severe scoliosis is a postural deformity caused by abnormal fixation of the fetus to the placenta. They also cite the high incidence of internal structural defects such as cardiac anomalies, unilateral absence of a kidney, or intestinal atresia, which do not fit with simple amnion rupture.

The fetal malformations that can occur as a result of ABS can be categorized into neural-tube–like defects, craniofacial anomalies, limb anomalies, and constrictive bands (Ho and Liu 1987; Lubinsky et al. 1983; Seeds et al. 1982; Seidman et al. 1989). The neural-tube–like defects include cases of anencephaly and encephalocele, which may be asymmetric or multiple. The craniofacial anomalies include facial clefts, nasal deformity, asymmetric microphthalmia, and abnormal cranial calcification. Limb anomalies may be multiple and asymmetric, including limb or digital amputation, pseudosyndactyly, abnormal dermatoglyphics, and some cases of clubbed feet. Abdominal-wall and thoracic-wall defects can occur and some cases are mistaken for gastroschisis or omphalocele with rupture.

The most puzzling component of the ABS is its association with visceral anomalies, including bladder exstrophy, vertebral hypoplasia, and other renal, gonadal, cardiac, and pulmonary defects (Bamforth 1992). Constrictive bands involving the extremities are the most common defect associated with the ABS (Huang et al. 1995).

The variation in manifestations of the ABS are thought to be due to differences in timing of amniotic rupture and the degree to which the fetus becomes entangled by strands of amnion (Higginbottom et al. 1979; Seeds et al. 1982). The effects the amniotic bands have on the developing fetus have been classified into malformation, disruption, and deformation (Higginbottom et al. 1979). Amniotic bands that interrupt the normal sequence of embryologic development lead to malformations such as cleft lip and palate, and abdominal-wall defects. In contrast, bands may tear normally developed structures, leading to disruption such as central nervous system or calvarial defects, acrosyndactyly, amputations and nonanatomical facial clefts (Lockwood et al. 1989). The effects of fetal compression and tethering may lead to deformations such as clubbing of the feet and angulation of the spine.

The timing of amnion rupture has been suggested to occur between 28 days after conception to 18 weeks of gestation. If amnion rupture occurs prior to 45 days of gestation, the results are likely to be devastating, including severe skull defects and major visceral defects (Huang et al. 1995). Rupture occurring after 45 days of gestation is likely to result in more limited defects.

The cause of amnion rupture and band formation is not well understood, but it has been observed following amniocentesis (Rehder 1978). Late gestation bands, even in the absence of an amniocentesis, can also occur. Lage et al. (1988) reported ABS presenting at birth with multiple abnormalities of the extremities despite a normal sonographic appearance at 21 weeks of gestation. There have also been cases of ABS associated with underlying disease. Young et al. (1985) reported two cases in fetuses with Ehlers–Danlos syndrome type IV and one with osteogenesis imperfecta. They speculated that the premature amnion rupture may have been due to reduced or abnormal collagen in the amnion. There have been rare familial cases of ABS, and some teratogens, such as lysergic acid diethylamide and methadone, have been reported in association with the syndrome (Chemke et al. 1973; Daly et al. 1996; Lubinsky et al. 1983).

Chorioamniotic separation, occurring spontaneously or as a consequence of invasive procedures, is a potential cause of the amniotic band syndrome. The incidence of chorioamniotic separation diagnosed by ultrasound is reported to range from 1 in 187 to 1 in 4333 births (Borlum 1989; Kaufman et al. 1985). The natural history of chorioamniotic separation occurring in normal pregnancies was initially thought to be benign. However, Graf et al. (1997) reported a case of chorioamniotic separation that resulted in the formation of amniotic bands involving the umbilical cord, resulting in fetal death. The incidence of chorioamniotic separation may be even higher in cases of fetal surgery. In the same report Graf and colleagues described 5 cases of chorioamniotic separation occurring in a series of 40 patients undergoing open fetal surgery. Three of the 5 fetuses had amniotic bands involving the umbilical cord, leading to fetal death in 1. This report speculated that because the amnion is adherent and fixed to the umbilical cord, once formed amniotic bands may retract to the cord, causing strangulation. Heifetz (1984), in a review of amniotic band syndrome, reported that as many as 10% of cases had umbilical-cord strangulation.

ABS is often misdiagnosed, especially in cases of early amniotic band rupture. Infants affected by early amniotic rupture present with anencephaly, encephalocele, abdominal- or thoracic-wall defects, and severe limb abnormalities. The severity of the anomalies obscures the cause, especially if the amniotic bands are not evident at birth. It has been estimated that a correct neonatal diagnosis of ABS is made in only 24 to 50% of patients without specialized genetic consultation (Seeds et al. 1982).

Regarding fetal treatment for amniotic band syndrome, the indications for fetal surgery are, with few exceptions, only for life-threatening conditions such as congenital pulmonary airway malformation (CPAM) with hydrops, congenital diaphragmatic hernia (CDH) with a low lung: heart ratio, bladder-outlet obstruction with oligohydramnios, or sacrococcygeal teratoma with placentomegaly. However, as experience with the techniques of fetal surgery has grown and the natural histories of certain non-life-threatening conditions have been better defined, the indications for fetal surgery have been extended. Two examples of this are in utero repair of meningomyelocele to prevent the devastating neurologic injury to the spinal cord (Adzick et al. 1998) and fetoscopic cord ligation in monochorionic twins with the imminent death of one twin to prevent neurologic injury in the surviving twin (Crombleholme et al. 1996). The indications for fetal surgery in the amniotic band syndrome may be either for a life-threatening condition if it involves constriction of the umbilical cord, or more commonly, threatened limb amputation due to amniotic band constriction (Keswani et al. 2003; Crombleholme 2001; Ashkenazy et al. 1982; Kanayama et al. 1995; Tadmor et al. 1997; Torpin 1965).

Torpin (1965) reported 36 cases of fetal death due to cord constriction from amniotic bands. In each case the diagnosis was made retrospectively, however. Recognition of amniotic bands constricting the umbilical cord has been reported by Kanayama et al. (1995), who were able to document fetal compromise by reversal of diastolic flow in the umbilical artery by color Doppler. It is in cases like the one reported by Kanayama et al. that fetoscopic lysis of amniotic bands could be lifesaving.

Based on their experience with fetoscopy for cord ligation in TRAP sequence and the experimental work by Crombleholme et al. demonstrating the potential for functional recovery of banded extremities once released, Quintero et al. performed the first fetoscopic lysis of amniotic bands in human fetuses (Crombleholme et al. 1995; Quintero et al. 1997). Their first case was a fetus at 21 weeks of gestation with bilateral cleft lip and bands attached to the face and left upper extremity with distal limb edema. In order to avert limb amputation, fetoscopic lysis of bands was attempted at 22 weeks of gestation using a two-port technique. However, due to bleeding encountered on insertion of the second operating port, it was removed. The endoscissors were passed through the port used for the fetoscope, and the lysis was performed under ultrasound guidance. There was resolution of the distal edema within 6 days of the procedure. At 32 weeks, microphthalmia and anophthalmia of the right orbit were first noted at the site of the previously attached amniotic band. The infant was delivered at 39 weeks and was found to have a type IV Tessier craniofacial cleft and right microphthalmia. The extremity showed minimal residual scarring where the band had been attached and lysed. The infant’s hand had radial paresis and mild hypoplasia.

The second case was a fetus at 23 weeks of gestation with a thick amniotic band constricting the left ankle of the fetus. There was marked edema distal to the band and minimal blood flow to the foot was observed by color and pulsed Doppler. Fetoscopy was performed using a 2.7-mm 5-degree endoscope and confirmed the sonographic findings. Again, bleeding was encountered on insertion of the operating port, necessitating its removal. Attempts at ultrasound-guided lysis using endoscissors were unsuccessful. A 2.4 mm 0-degree operating scope with a 400-µm contact YAG laser fiber was used to lyse approximately 85% of the band. Complete lysis of the band was not achieved for fear of injury to “important elements in the ankle.” Postoperatively, the edema markedly improved, as did distal arterial blood flow, and there was return of flexion and extension on follow-up sonographic examination. The mother was hospitalized 8 weeks postoperatively at 31 weeks of gestation with premature rupture of membranes and delivered at 34.5 weeks of gestation. The infant underwent Z-plasties for residual effects of the amniotic band, and full functional recovery was anticipated.

The rationale for performing fetoscopic lysis of constricting extremity amniotic bands is based on the hypothesis that progressive compromise of fetal growth leads to amputation. However, this assumes that the procedure can be accomplished with no maternal morbidity and minimal fetal morbidity. This procedure would be hard to justify in the face of a serious maternal complication or a fetal death due to severely premature delivery at 21 or 23 weeks of gestation, even in the face of certain fetal limb amputation.

The experience reported by Keswani et al. (2003) similarly supports the use of fetoscopic release of amniotic bands for limb salvage. However, the sequelae of the ABS may not completely remove or may result in secondary lymphedema. It is worth noting that the cases reported all had additional amniotic bands encircling limbs not appreciated by ultrasound which were also lysed. Crombleholme has experience with fetoscopic release of amniotic bands involving the umbilical cords in 3 fetuses (Crombleholme, unpublished observation 2008). All were successfully lysed with all 3 surviving

While extremity ABS may have devastating morphologic and functional effects on a limb, possibly resulting in amputation, it is not lethal. Extremity ABS is not an indication for fetoscopic surgery unless maternal risks and incidence of preterm labor are fully appreciated by the mother. However, there are forms of ABS that are lethal or have devastating neurologic sequelae that may justify the current risks of intervention. Torpin (1965) has reported 36 cases of constrictive amniotic bands of the umbilical cord, which were uniformly fatal. Although rarer than other forms of ABS, umbilical-cord constriction, once diagnosed sonographically, may be amenable to fetoscopic release to avert fetal death as shown by Crombleholme (unpublished observation 2008).

In managing a pregnancy with suspected Amniotic Band Syndrome it is essential to have a detailed sonographic fetal survey to accurately assess any anomalies present. Fetal echocardiography is indicated in cases of abdominal wall or abdominothoracic wall defects because of the increased incidence of associated cardiac defects. Amniocentesis is not necessary in clear-cut cases of ABS as these are sporadic deformations with no association with chromosomal abnormalities. However, in instances in which the diagnosis is uncertain, genetic amniocentesis should be considered. For example, in cases of abdominal wall defects in which a ruptured covered omphalocele cannot be excluded, genetic amniocentesis is indicated.

A fetus with ABS should pose no increased risk for the mother in the management of the pregnancy. There is no indication for cesarean section, except for obstetrical indications. In severe cases of ABS, such as LBWC, in which survival is not anticipated, conventional labor and vaginal delivery without intervention for fetal distress should be considered.

Amniotic band syndrome surgery usually begins after birth, unless it's been deemed life threatening. A fetus known to have amniotic band syndrome should be delivered in a tertiary-care center with neonatologists, pediatric surgeons, and pediatric plastic and orthopedic surgeons available. Treatment depends on the nature of the amniotic band syndrome and the severity of the deformation. In cases of umbilical-cord involvement, early or even emergency delivery may be indicated if there are signs of fetal compromise (Kanayama et al. 1995).

After delivery a careful physical examination should assess the severity of the amniotic band syndrome. Often there will be no evidence of the amniotic band at the time of delivery. In the case of extremity amniotic bands, treatment is dictated by the severity of the deformation. The severity of deformity can range from a mildly constrictive band, requiring a release, to near amputation, requiring debridement. More often there is a band-like deformation that requires Z-plasties to surgically correct (Findik et al. 2006; Dyer and Chamlin 2005).

In cases of amniotic bands involving the face and head, there may be severe facial clefts, anophthalmia, and encephalocele. These deformities may require many extensive reconstructive procedures to achieve an acceptable cosmetic result. Cases of the LBWC form of amniotic band syndrome are always fatal, and no reconstructive procedures are indicated.

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