Amniotic band syndrome is a group of congenital anomalies involving limbs, craniofacial region, or trunk.
Amniotic band syndrome can range from constrictive bands involving a digit to thoracoabdominoschisis, encephalocele, or the limb–body wall complex.
The incidence ranges widely from 1 in 1200 to 1 in 15,000 livebirths depending on how it is defined.
Ultrasound examination is the mainstay of diagnosis.
Amniotic bands can occur spontaneously or as a result of instrumentation of the pregnancy.
Fetoscopic release of amniotic bands may prevent limb amputation when it involves an extremity or may be lifesaving if they involve the umbilical cord.
Almost all cases of amniotic band syndrome deliver prematurely.
The amniotic band syndrome (ABS) is a group of sporadic congenital anomalies that involve the limbs, craniofacial regions, and trunk, ranging from constrictive bands, pseudosyndactyly to amputation, as well as multiple craniofacial, visceral, and body wall defects (Torpin, 1965; Jones et al., 1974; Higginbottom and Jones, 1979; Seeds et al., 1982; Ray et al., 1988; Lockwood et al., 1989; Seidman et al., 1989; Kulkarni and Gopal, 1990). The term amniotic band syndrome encompasses many congenital anomalies, including amniotic band disruption complex (Higginbottom and Jones, 1979), amniochorionic mesoblastic fibrous strings (Torpin, 1965), aberrant tissue bands (Jones et al., 1974), amniotic deformity, adhesion and mutilation (ADAM) complex (Keller et al., 1978; Orioli et al., 2003), amniotic adhesion malformation syndrome (Herva and Karkinen-Jaaskelainen, 1984), and the limb and/or body wall defect (Bamforth, 1992).
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 (Keller et al., 1978; Higginbottom and Jones, 1979; Seeds et al., 1982; Herva and Karkinen-Jaaskelainen, 1984).
More recently, Moerman et al. (1992) proposed that the ABS is a collection of three distinct entities that can reconcile both 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) (see Chapter 60). 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 and Simon, 1963; Torpin, 1965). These authors distinguish cases caused by constrictive bands from those caused by broad amniotic adhesions. Moerman et al. (1992) 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 clubfoot. Non-band-related defects occur as a result of vascular disruptions or from compression (Miller et al., 1981). The thoracoabdominoschisis of LBWC is characterized by an anterolateral body wall defect with evisceration of abdominal and/or thoracic organs. The eviscerated organs are in an extra-amniotic 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 tubelike defects, craniofacial anomalies, limb anomalies, and constrictive bands (Seeds et al., 1982; Lubinsky et al., 1983; Ho and Liu, 1987; Seidman et al., 1989). The neural tubelike 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 and Jones, 1979; Seeds et al., 1982). The effects the amniotic bands have on the developing fetus have been classified into malformation, disruption, and deformation (Higginbottom and Jones, 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; Lubinsky et al., 1983; Daly et al., 1996). Other significant exposures include misoprostol and maternal fever (Orioli et al., 2003; Ribeiro et al., 2004).
Chorioamniotic separation, occurring spontaneously or as a consequence of invasive procedures, is a potential cause of the ABS. The incidence of chorioamniotic separation diagnosed by ultrasound is reported to range from 1 in 187 to 1 in 4333 births (Kaufman et al., 1985; Borlum, 1989). 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 five fetuses had amniotic bands involving the umbilical cord, leading to fetal death in one. 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 ABS, 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).
Because of difficulties in accurately diagnosing ABS, the estimates of its incidence vary widely. The reported incidence ranges from 1 in 1200 to 1 in 15,000 livebirths (Chemke et al., 1973; Seeds et al., 1982; Ho and Liu, 1987; Ray et al., 1988). More recent estimates place the incidence of ABS at 1 in 1200 because of the more frequent recognition of an amniogenic cause for congenital anomalies (Ossipoff and Hall, 1977; Seeds et al., 1982; Moerman et al., 1992). In a retrospective analysis of 3173 autopsies performed during a 14-year period, Czichos et al. (2005) found 744 cases of malformations of which 14 had anomalies thought to be a consequence of amnion rupture. This series yielding an incidence of 1:226 among fetuses and newborns undergoing autopsy suggested that it may be a more common cause of anomalies than generally appreciated.
Hands are more frequently affected than feet, with the largest fingers (third, fourth, and second) more commonly afflicted (Ribeiro et al., 2004).
ABS 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 endovaginal probe. The bands can be extremely difficult to detect sonographically and ABS is more often diagnosed by the effect that they have on fetal anatomy (Figure 100-1). 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) (Figure 100-2). 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 (Figure 100-3). 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 (Figure 100-3). However, prenatal diagnosis is the exception rather than the rule.
Sonographic image demonstrating an amniotic band attached to the fetus and floating in the amniotic fluid.
Sonographic image of a fetus with a constricting amniotic band of an extremity. A. 2-D image depicting amputation of the distal portion of both lower extremities as a result of amniotic bands. B. 2-D image of the same fetus showing bilateral limb reduction defects.
Sonographic image of a fetus with amniotic band syndrome manifesting as A. a “slash” defect in the maxillary region, and B. an eccentric encephalocele. C.Amniotic bands were also noted to be attached to the extremities (arrowheads). (Reprinted, with permission, from Filly RA, Golbus MS. The fetus with amniotic band syndrome. In: Harrison MR, Golbus MS, Filly RA, eds. The Unborn Patient. 2nd ed. Philadelphia, PA: WB Saunders; 1991:440-447.)
The findings in ABS may be limited to isolated defects, including isolated facial cleft, digital amputation, or mild elephantiasis of an extremitybeyond 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.
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 slashlike 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 LBWC form of ABS (Figure 100-4).
Sonographic image of a fetus with limb–body wall complex showing severe twisting deformity of the spine associated with gastropleuroschisis and amniotic bands attached to the extremities. A. The fetal spine (Sp) has a severe twisting deformity. B. The twisting deformity is so severe that the viscera (VE) herniated through the gastropleuroschisis are found posterior to the fetus. C. The amnion (arrows) encircles the exteriorized viscera. (Reprinted, with permission, from Filly RA, Golbus MS. The fetus with amniotic band syndrome. In: Harrison MR, Golbus MS, Filly RA, eds. The Unborn Patient. 2nd ed. Philadelphia, PA: WB Saunders; 1991:440-447.)
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 (see Chapter 7). 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 (Sauerbrei et al., 1980; Burrows et al., 1982; Patten et al., 1986).
Chorioamniotic separation may occur as a result of amniocentesis or fetal surgery, and extrachorionic hemorrhage may separate the chorioamniotic membrane from the uterine wall (Spirit et al., 1979; Burrows et al., 1982; Graf et al., 1997). In both of these instances, a membrane may be observed sonographically. Other causes of membranes in the developing fetus include septate uterus, blighted twin, and circumvallate placenta (Filly and Golbus, 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 and Zourlas, 1969; Mahony et al., 1985; Randal et al., 1988; Filly and Golbus, 1991). 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 growth of the fetus. Filly and Golbus (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, because of rupture or compression by the growing fetus.
In the LBWC there is a constellation of abnormalities, including myelomeningocele or caudal regression, thoracoabdominoschisis, or abdominoschisis and limb defects (see Figure 100-4). 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 thoracoabdominoschisis. Facial clefts may also be seen in LBWC.
ABS involving the umbilical cord can be recognized by abnormal clustering of loops of 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 (Figure 100-5).
A. Sonographic image of amniotic bands involving the umbilical cord and the right upper extremity. B. Color doppler of the same patient.
The differential diagnosis in ABS depends on the sonographic findings. In isolated constrictive amniotic bands associated with distal limb edema, possible lymphatic or vascular malformations should be considered. However, color Doppler studies should closely show the flow characteristics of a vascular malformation. Constrictive bands involving the upper extremity should suggest the possibility of the VACTERL association if the radius is affected, and Fanconi anemia if radial hypoplasia or absent thumbs are observed. Amniotic membranes within the amniotic cavity without associated fetal anomalies may be amniotic sheets secondary to intrauterine synechiae or remnant of a blighted twin, or secondary to amniocentesis or chorionic villus sampling.
A diagnosis of LBWC requires two of three of the following abnormalities: (1) myelomeningocele or caudal regression, (2) abdominal or thoracoabdominal wall defect, or (3) limb defects. The main differential diagnoses are cases of isolated neural tube defects or ruptured omphalocele, which do not meet the criteria for LBWC. The body stalk anomaly has a similar constellation of anomalies but the placenta is attached to the trunk of the fetus.
ANTENATAL NATURAL HISTORY
There is great controversy about the pathogenesis of the various forms of ABS. Part of this controversyinvolves 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 (Figures 100-2, 100-6, and 100-7) (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 (Torpin, 1965; Kanayama et al., 1995; Graf et al., 1997). However, the poorly characterized pathogenesis of this syndrome and limited sonographic surveillance, limit our understanding of its prenatal natural history.
3D image demonstrating absence of the left fetal hand in a pregnancy complicated by amniotic bands.
Plain radiograph of the right leg of a newborn who sustained amputation in utero of the right leg and foot from amniotic bands. (Courtesy of Benjamin Alman, MD)
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 initiallynormal 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 (Torpin, 1965; Moerman et al., 1992). 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.
In managing a pregnancy with suspected ABS, 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.
The indications for fetal surgery are, with few exceptions, only for life-threatening conditions such as congenital pulmonary airway malformation (CPAM) with hydrops, diaphragmatic hernia with a low lung-to-heart ratio, bladder outlet obstruction with oligohydramnios, or sacrococcygeal teratoma with placentomegaly (see Chapters 35, 37, 38, 82, and 115). 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 imminent death ofone twin to prevent neurologic injury in the surviving twin (Crombleholme et al., 1996). The indications for fetal surgery in the ABS 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 (Torpin, 1965; Ashkenazy et al., 1982; Kanayama et al., 1995; Quintero et al., 1997; Tadmor et al., 1997; Crombleholme, 2001; Keswani et al., 2003).
Torpin (1965) reported 36 cases of fetal death due to cord constriction from amniotic bands. In each case, the diagnosis was made retrospectively. 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.
On the basis of 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, because of 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 offetoscopic release ofamniotic 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 that all had additional amniotic bands encircling limbs not appreciated by ultrasound examination that were also lysed. Crombleholme has experience with fetoscopic release of amniotic bands involving the umbilical cords in five fetuses (Crombleholme TM, unpublished observation, 2009). All were successfully lysed with all three fetuses surviving the procedure.
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).
A fetus known to have ABS 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 ABS 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 ABS. 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 release, to near amputation, requiring debridement. More often there is a bandlike deformation that requires Z-plasties to surgically correct it (Dyer and Chamlin, 2005; Findik et al., 2006) (Figure 100-8).
A. Postnatal appearance of the leg of a newborn with extremity amniotic band syndrome. B. Postnatal appearance of the hand of a newborn with extremity amniotic band syndrome.
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 ABS are always fatal, and no reconstructive procedures are indicated.
The outcome in ABS depends on the severity of the deformation. Cases of extremity ABS usually have an excellent long-term outcome. Even in cases of limb amputation, ambulation is possible with the aid of a prosthesis. The cosmetic results following extensive craniofacial reconstructive surgery are often acceptable, but the severity of these defects may leave these children permanently disfigured. ABS in which fetoscopic release was performed may show evidence of secondary lymphedema, which may require multiple surgical procedures to provide an acceptable functional result (Marler et al., 2002).
GENETICS AND RECURRENCE RISK
Most cases of ABS are sporadic and there is no risk of recurrence in subsequent pregnancies. There have been cases of ABS associated with underlying disease, such as Ehlers–Danlos syndrome type III or osteogenesis imperfecta. Similarly, ABS has been reported in association with teratogens such as methadone and lysergic acid diethylamide (Chemke et al., 1973; Daly et al., 1996). While associated maternal disease or teratogenic exposure may predispose to recurrence, these are rare causes of the ABS.
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