- Email: [email protected]
The amniotic band syndrome: Antenatal sonographic diagnosis and potential pitfalls
The amniotic band syndrome: Antenatal sonographic diagnosis and potential pitfalls Barry S. Mahony, M.D., Roy A. Filly, M.D., Peter W. Callen, M.D., and Mitchell S. Golbus, M.D. San Francisco, California Amniotic band syndrome causes a variety of fetal malformations involving the limbs, craniofacial region, and trunk. Six prenatally diagnosed cases of amniotic band syndrome are discussed. The diagnosis was based on sonographic visualization of either amniotic sheets or bands associated with fetal deformation or deformities in nonembryologic distributions known to characterize the amniotic band syndrome. Seven additional cases are considered in which an aberrant sheet of tissue with a free edge was visualized within the amniotic cavity but no restriction of fetal motion or subsequent deformity was demonstrated. (AM J CasTET GVNECOL 1985;152:63-8.)
Key words: Amniotic band syndrome, sonography, fetal malformations
The amniotic band syndrome is a common, nonrecurrent cause of various fetal malformations involving the limbs, craniofacial region, and trunk. I Recent reports indicate that the incidence of the amniotic band syndrome approximates one per 1200 live births and that many neonates with the amniotic band syndrome have been diagnosed incorrectly as having other forms of congenital malformations. I. 2 Documentation of characteristic features, including clefts and malformations in nonembryologic distributions, asymmetric encephaloceles, and gastropleural schisis, can be suggestive of the amniotic band syndrome even when the bands that caused these deformities are not apparent. Although sonography permits antenatal visualization of typical features of the amniotic band syndrome, to our knowledge in only one case of amniotic band syndrome has the sonographic diagnosis been made before birth.' In one additional case the sonographic documentation of "discordant" anencephaly in a twin pregnancy alerted the obstetrician to the presence of congenital deformity, but the antenatal diagnosis of the amniotic band syndrome was not rendered.' Advances in sonographic resolution capabilities now permit frequent visualization of membranes or membrane-like structures within the uterus (Fig. 1). For example, segments of amniotic membrane that have not yet fused with the chorion can be visualized normally in the first 16 weeks of gestation.' Also, subamniotic and subchorionic fluid collections occurring at anytime From the Departments of Radiology and Obstetrics, Gynecology, and Reproductive Sciences, University of California (San Francisco) School of Medicine. Received for publication May 7,1984; revised October 12,1984; accepted December 17, 1984. Reprint requests: Roy A. Filly, M.D., University of California Medical Center, L-374, San Francisco, CA 94143.
during pregnancy may render these membranes visible. However, we have also observed aberrant sheets of tissue with a free edge that clearly project into the lumen of the amniotic cavity and may mimic "amniotic bands" but that do not result in the amniotic band syndrome (Fig. 2). Because the amniotic band syndrome is a sporadic disorder that may mimic recurrent disorders, appropriate genetic counseling requires accurate diagnosis. Conversely, when sonography visualizes an aberrant sheet of tissue with a free edge within the amniotic fluid, accurate assessment of normal fetal morphology avoids the false positive diagnosis of the amniotic band syndrome that might lead to termination of a potentially normal pregnancy. We herein report five additional cases of the amniotic band syndrome diagnosed before birth on the basis of sonographic visualization of either amniotic sheets or bands with associated fetal deformities or deformities in non embryologic distributions characteristic of the amniotic band syndrome. We also report seven infants without the amniotic band syndrome in whom antenatal sonography visualized an aberrant sheet of tissue with a free edge in the amniotic fluid but normal fetal morphologic features. Case material Table I summarizes the sonographic and follow-up data regarding the six cases in which the antenatal sonographic diagnosis of the amniotic band syndrome was made. Case 2 has been reported previously from this institution.' In two cases, an amniotic sheet or bands were seen attached to fetal parts and were associated with fetal edema, deformity, andlor restriction of motion (Fig. 3). In the other four cases, no aberrant sheets 63
64
Mahony et al.
Fig. 1. Examples of intrauterine membranes or membranelike structures that do not have a free edge within the amniotic fluid . The absence of a free edge distinguishes these structures from the aberrant sheets of tissue that may mimic amniotic bands. A, Portions of the amnion (arrow) that have not yet fused with the chorion are visible in this fetus at 11 menstrual weeks. B , A subchorionic lucency (L) compatible with extrachorionic hemorrhage extends to the edge of the placenta (P) (black arrow). The extrachorionic hemorrhage creates a membrane-like structure (white arrow) in this first-trimester pregnancy complicated by vaginal bleeding. C, and D, Lucency between the placenta (P) and the amnion (arrow head) produces a membrane-like structure without a free edge. This represents amniochorionic separation. or bands of tissue were seen in the amniotic fluid, possibly because of concomitant oligohydramnios, but characteristic deformities in nonembryologic distributions permitted the antenatal diagnosis of the amniotic band syndrome. Follow-up pathologic evaluation confirmed the presence of the amniotic band syndrome in each case. Table II provides analogous data regarding the seven cases in which we observed an aberrant sheet of tissue with a free edge in the amniotic fluid but no associated fetal deformity or entrapment (Fig. 2). Sheets of aberrant tissue were distinguished from other causes of intrauterine membranes by their free edge within the amniotic fluid. 5 In each case only a single sheet of aber-
May I , 1985 Am J Obstel Gynecol
Fig. 2. Real-time scans display an aberrant sheet of tissue with a free edge within the amniotic fluid (Case 9) . This pregnancy resulted in a normal infant. A, Although fetal parts (H = head, E = extremity) bridge the sheet of tissue (open arrow), there was no fetal deformity, edema, or restriction of motion. Note the broad base of the aberrant sheet of tissue (small closed arrow) . B, This scan plane sections longitudinally through the thickened free edge of the sheet of tissue (closed arrow) (H = head). C, In this plane of section, which images the aberrant sheet of tissue transversely, the sheet of tissue appears band like (open arrow). Again noted is its bulbous free edge (closed arrow) as well as the bridging fetal pans (H = head, E = extremity) . rant tissue was visible. In two insta nces a sheet of tissue that had been seen earlier in pregnancy was no longer visible later in pregnancy. Although the sheet of tissue touched five of the fetuses, in none did it appear attached to the fetus; the fetus was able to alter its position relative to the sheet of tissue. Similarly, although fetal
Amniotic band syndrome 65
Volume 152 Number I
Table I. Sonographic and follow-up data regarding the six cases in which diagnosis of amniotic band syndrome was made on basis of antenatal sonogram (case 2 has been reported previously3)
Case No.
Reason for sonography
Attached to or Menstrual Sheet or Single or touching Bridging age (wk) bands multiple fetus fetal parts
Associated edema, deformity
Amniotic sheet or bands associated with fetal deformity I Twins; anom21 Bands Multiple Attached Numerous Multiple facial clefts aly on outside sonogram (?) 21 Sheet Single Attached Numerous Asymmetric 2 Maternal edema drug abuse Fetal deformities in nonembryonic distributions; aberrant sheets or bands not visualized 3 Omphalocele 37 One leg on outside absent sonogram 4 Abnormalities on outside sonogram
25
5 Anomalies
22
6 Omphalocele on outside sonogram (?)
30
on outside sonogram (?)
parts intermittently bridged the aberrant sheet of tissue in three instances, in no case was there associated fetal deformity or restriction of motion. Each pregnancy resulted in an infant without evidence of the amniotic band syndrome. In Case 12, sonography also demonstrated evidence of alobar holoprosencephaly, a developmental anomaly not related to the amniotic band syndrome. Comment
Most contemporary authors concur with the hypothesis elaborated by Torpin 6 in 1968, which explains the characteristic clinical features of the amniotic band syndrome. I. ' ·5 . 7· 10 Torpin asserted that rupture of the amnion leads to subsequent entanglement of various embryonic or fetal parts by fibrous mesodermic bands that emanate from the chorionic side of the amnion. Entrapment of fetal parts by the bands may cause lymphedema, amputation, or slash defects in nonembryologic distributions. Torpin further suggested that the amnion, which is contiguous with the fetal skin at the umbilicus, protects the fetus from contact with the chorion. When disruption of the amnion occurs, the fetus may
One leg absent
Restriction of motion Other deformities Yes
Yes
Asymmetric encephalocele
Follow-up Amniotic band syndrome (autopsy)
No
Amniotic band syndrome (autopsy)
Gastroschisis with exteriorization of liver and bowel Gastropleu ral schisis with exteriorization of liver, bowel, and heart Gastropleu ral schisis with exteriorization of liver and heart, asymmetric encephalocele Gastroschisis with exteriorization of liver and bowel, marked scoliosis, small thorax
Amniotic band syndrome (autopsy) Amniotic band syndrome (autopsy) Amniotic band syndrome (autopsy)
Amniotic band syndrome (autopsy)
adhere to and fuse with the chorion with subsequent maldevelopment of the subjacent fetal tissue. Although the amniotic band syndrome manifests variable patterns of deformity, a proclivity for certain anomalies typifies the disorder and permits prenatal diagnosis. For example, exteriorization of the liver rarely occurs with gastroschisis. II. 12 However, in each of our four fetuses who had gastroschisis associated with the amniotic band syndrome, hepatic exteriorization occurred. This suggests that when gastroschisis results in exteriorization of the liver the amniotic band syndrome should be strongly considered. Similarly, approximately 90% of encephaloceles occur in the midline because of failure of neural tube fusion. 13 In both of our fetuses with an encephalocele associated with the amniotic band syndrome the encephalocele occurred laterally. Therefore, identification of an asymmetric encephalocele should strongly suggest the amniotic band syndrome, although asymmetric encephaloceles can occur without amniotic band syndrome. Other craniofacial malformations such as asymmetric anencephaly and bizarre clefting patterns should also suggest the amniotic band syndrome. Cleft
66
Mahony et al.
May I, 1985 Am J Obstet Gynecol
Fig. 3. Representative sonograms of a fetus (Case I) with the amniotic band syndrome. A, Scan through the fetal head demonstrates an asymmetrical encephalocele (solid arrows) (F = falx cerebri). S, Numerous bands (arrows) are attached to the fetal extremities (E) and restrict fetal motion. Other scans showed facial clefts in a nonembryologic distribution. These features enabled an antenatal diagnosis of the amniotic band syndrome.
ion
Amnio~I---+---j
,H---!-IPalrti(JI uterine septation
Fig. 4. Schematic drawing of the gravid uterus. Amnion and chorion extend over a uterine synechia or partial septation. This creates a sheet of aberrant tissue with a free edge within the amniotic fluid. Despite the "free" edge, the amnion is not disrupted. Although fetal parts may bridge or touch the aberrant sheet of tissue, there is no associated fetal deformity or restriction of motion. This appearance is not associated with the amniotic band syndrome.
lip and palate are common paramedian or median malformations that occur in characteristic patterns caused by failure of fusion of the paraxial mesodermic masses. 14 Although they may occur in association with other congenital anomalies, there is no reported in-
creased incidence with asymmetric encephaloceles, gastropleural schisis, or multiple amputations. On the other hand, facial fissures associated with the amniotic band syndrome form in bizarre, nonembryologic patterns.
Amniotic band syndrome 67
Volume 152 Number I
Table II. Sonographic and follow-up data regarding the seven cases in which an aberrant sheet of tissue with a free edge in the amniotic fluid was present but there were no associated fetal deformities Attached to Associated edema, Restriction Single or or touching Bridging f etal parts deformity of motion fetus multiple
Other deformities
Follow-up
None
None
Normal infant
None None
None None
None None
Normal infant
None None
None None
None None
None None
Normal infant
Leg
None
None
None
None
None
None
None
None
None
None
None
Normal infant
None
None
None
Normal infant
None
None
None
Normal infant
None
None None None
None None None
None
None
None
Reason for sonogram
Menstrual age (wk)
Sheet or bands
7
Size-dates discrepancy
13
Sheet
Single
Touching fetus
None
None
8
Previous holoprosencephaly
21 19
Not visible Sheet
Single
Extremity, trunk
Head
9
Maternal age (35 yr)
25, 29, 38 17
Sheet Sheet
Single Single
Neither Neither
20
Sheet
Single
23-33 (every 2-5 wk) 34
Sheet
Single
Touching neck Neither
Sheet
Single
Neither
17
Sheet
Single
Neither
23
Sheet
Single
25, 29 32 29
Sheet Not visible Sheet
Single Single
Touching occiput
20
Sheet
Single
Neither
Case No.
10 II
Previous fetal death Size-dates discrepancy
12
Maternal diabetes
13
Amniotic band on outside sonogram
Umbilical cord Touching None legs, trunk Neither None
None None Stillborn at 30 Alobar menstrual holoprosencephaly weeks with alobar holoprosencephaly, otherwise normal Normal None
(?)
Although extremity amputations may result from genetic or teratogenic causes, several distinguishing features permit identification of amputations related to the amniotic band syndrome.6 Whereas genetic or teratogenic amputations tend to be bilaterally symmetrical, amputations caused by the amniotic band syndrome are usually asymmetric. While syndactyly that involves the base of the digits implies genetic or teratogenic causes, syndactylism that originates distally suggests the amniotic band syndrome. Identification of a fibrous band of tissue within a constricting ring with distal elephantiasis or protrusion of uncovered bone distal to the soft tissue at the site of amputation constitute pathognomonic signs of the amniotic band syndrome. Such fibrous bands also can be found when facial fissures are caused by this syndrome. Constriction of the umbilical cord by an amniotic band represents potential "amputation" at its most extreme. Among 36 fetuses with umbilical cord constriction identified by Torpin,6 none survived.
When antenatal sonography visualizes an aberrant sheet or bands of tissue attached to a fetus with characteristic deformities and restriction of motion , a diagnosis of the amniotic band syndrome can be made. Even when the aberrant sheets or bands are not visualized, characteristic fetal deformities in nonembryologic distributions provide evidence highly suggestive of the amniotic band syndrome. Such information will alert the perinatalogist and geneticist to obtain a detailed postnatal examination. On confirmation of the diagnosis, appropriate counseling can be performed. The recurrence risk for the aberrant bands and any consequences thereof appear to be negligible. 1O Aberrant sheets of tissue with a free edge within the amniotic fluid often occur in the absence of the amniotic band syndrome. During Torpin's" extensive review of 400 fetuses with amnion rupture, he discovered only three cases in which the fetus escaped injury. In contrast, all seven of the pregnancies in the current study in which we visualized a single aberrant sheet of tissue
68 Mahony et al.
within the amniotic fluid but no associated fetal deformity resulted in infants without the amniotic band syndrome. The sonographically visible aberrant tissue within the amniotic fluid in these cases may represent intact amnion and chorion extending over a partial uterine septation or synechia (Fig. 4). That the base or free edge of the aberrant sheet of tissue often appeared disproportionately thickened supports this hypothesis. Furthermore, we are aware of an additional case with similar findings in a woman with uterine synechia documented by hysterosalpingography (Rich P, personal communication). Finally, in two instances the aberrant sheet disappeared as the uterus enlarged. Possible explanations of this sequence are that a synechia was stretched beyond its tensile strength, permitting rupture and disappearance of the observed abnormality, or that the sheet was simply compressed against the uterus by growth of the fetus and thus became imperceptible. In the above-described seven cases there would be no chance for fetal entanglement and only a very small chance for entrapment of fetal parts. Therefore antenatal sonographic demonstration of a sheet of aberrant tissue in the amniotic fluid surrounding a fetus without evidence of associated deformity does not imply the presence of the amniotic band syndrome. This finding alone does not constitute sufficient indication for elective pregnancy termination. REFERENCES I. Seeds JW, Cefalo RC, Herbert WNP. Amniotic band syndrome. AM J OBSTET GVNECOL 1982; 144:243.
May I, 1985 Am J Obstet C ynecol
2. OssipoffV, Hall BD. Etiologic factors in the amniotic band syndrome: a study of twenty-four patients. Birth Defects 1977;13:117. 3. Fiske CE, Filly RA, Golbus MS. Prenatal ultrasound diagnosis of amniotic band syndrome. J Ultrasound Med 1982;1:45. 4. Worthen NJ, Lawrence D, Bustillo M. Amniotic band syndrome: antepartum ultrasonic diagnosis of discordant anencephaly. JCU 1980;8:453. 5. Burrows PE, Lyons EA, Phillips HJ , et al. Intrauterine membranes : Sonographic findings and clinical significance. JCU 1982;10:1. 6. Torpin R. Fetal malformations caused by amnion rupture during gestation. Springfield, Illinois: Charles C Thomas, 1968:1-76. 7. Rushton DI. Amniotic band syndrome. Br Med J 1983; 286:919. 8. Moessinger AC, Blanc WA, Byrne J , et al: Amniotic band syndrome associated with amniocentesis. AM J OBSTET GVNECOL 1981;141 :588. 9. Miller ME, Graham JM , Higginbottom MC, et at. Compression-related defects from early amnion rupture: evidence for mechanical teratogenesis. J Pediatr 1981 ;98: 292. 10. Higginbottom MC,Jones KL, Hall BD, et at. The amniotic band disruption complex : timing of amniotic rupture and variable spectra of consequent defects. J Pediatr 1979;95: 544. II . Nakayama DK. Management of the fetus with an abdominal wall defect. In: Harrison MR, Golbus MS, Filly RA, eds. The unborn patient: prenatal diagnosis and treatment. Orlando: Grune & Stratton Inc. , 1984:217-34. 12. Raffensperger JG. Gastroschisis. In : Nyhus LM, Condon RE, eds. Hernia, ed 2. Philadelphia: J B Lippincott, 1978:357-61. 13. Fink Ij, ChiDn DH, Callen pw. A potential pitfall in the ultrasonographic diagnosis of fetal encephalocele. J Ultrasound Med 1983;2:31 3. 14. LongacreJ]. Cleft palate d eformation : causation and prevention. Springfield, Illinois : Charles C Thomas, 1970: 104.
Key words: Amniotic band syndrome, sonography, fetal malformations
The amniotic band syndrome is a common, nonrecurrent cause of various fetal malformations involving the limbs, craniofacial region, and trunk. I Recent reports indicate that the incidence of the amniotic band syndrome approximates one per 1200 live births and that many neonates with the amniotic band syndrome have been diagnosed incorrectly as having other forms of congenital malformations. I. 2 Documentation of characteristic features, including clefts and malformations in nonembryologic distributions, asymmetric encephaloceles, and gastropleural schisis, can be suggestive of the amniotic band syndrome even when the bands that caused these deformities are not apparent. Although sonography permits antenatal visualization of typical features of the amniotic band syndrome, to our knowledge in only one case of amniotic band syndrome has the sonographic diagnosis been made before birth.' In one additional case the sonographic documentation of "discordant" anencephaly in a twin pregnancy alerted the obstetrician to the presence of congenital deformity, but the antenatal diagnosis of the amniotic band syndrome was not rendered.' Advances in sonographic resolution capabilities now permit frequent visualization of membranes or membrane-like structures within the uterus (Fig. 1). For example, segments of amniotic membrane that have not yet fused with the chorion can be visualized normally in the first 16 weeks of gestation.' Also, subamniotic and subchorionic fluid collections occurring at anytime From the Departments of Radiology and Obstetrics, Gynecology, and Reproductive Sciences, University of California (San Francisco) School of Medicine. Received for publication May 7,1984; revised October 12,1984; accepted December 17, 1984. Reprint requests: Roy A. Filly, M.D., University of California Medical Center, L-374, San Francisco, CA 94143.
during pregnancy may render these membranes visible. However, we have also observed aberrant sheets of tissue with a free edge that clearly project into the lumen of the amniotic cavity and may mimic "amniotic bands" but that do not result in the amniotic band syndrome (Fig. 2). Because the amniotic band syndrome is a sporadic disorder that may mimic recurrent disorders, appropriate genetic counseling requires accurate diagnosis. Conversely, when sonography visualizes an aberrant sheet of tissue with a free edge within the amniotic fluid, accurate assessment of normal fetal morphology avoids the false positive diagnosis of the amniotic band syndrome that might lead to termination of a potentially normal pregnancy. We herein report five additional cases of the amniotic band syndrome diagnosed before birth on the basis of sonographic visualization of either amniotic sheets or bands with associated fetal deformities or deformities in non embryologic distributions characteristic of the amniotic band syndrome. We also report seven infants without the amniotic band syndrome in whom antenatal sonography visualized an aberrant sheet of tissue with a free edge in the amniotic fluid but normal fetal morphologic features. Case material Table I summarizes the sonographic and follow-up data regarding the six cases in which the antenatal sonographic diagnosis of the amniotic band syndrome was made. Case 2 has been reported previously from this institution.' In two cases, an amniotic sheet or bands were seen attached to fetal parts and were associated with fetal edema, deformity, andlor restriction of motion (Fig. 3). In the other four cases, no aberrant sheets 63
64
Mahony et al.
Fig. 1. Examples of intrauterine membranes or membranelike structures that do not have a free edge within the amniotic fluid . The absence of a free edge distinguishes these structures from the aberrant sheets of tissue that may mimic amniotic bands. A, Portions of the amnion (arrow) that have not yet fused with the chorion are visible in this fetus at 11 menstrual weeks. B , A subchorionic lucency (L) compatible with extrachorionic hemorrhage extends to the edge of the placenta (P) (black arrow). The extrachorionic hemorrhage creates a membrane-like structure (white arrow) in this first-trimester pregnancy complicated by vaginal bleeding. C, and D, Lucency between the placenta (P) and the amnion (arrow head) produces a membrane-like structure without a free edge. This represents amniochorionic separation. or bands of tissue were seen in the amniotic fluid, possibly because of concomitant oligohydramnios, but characteristic deformities in nonembryologic distributions permitted the antenatal diagnosis of the amniotic band syndrome. Follow-up pathologic evaluation confirmed the presence of the amniotic band syndrome in each case. Table II provides analogous data regarding the seven cases in which we observed an aberrant sheet of tissue with a free edge in the amniotic fluid but no associated fetal deformity or entrapment (Fig. 2). Sheets of aberrant tissue were distinguished from other causes of intrauterine membranes by their free edge within the amniotic fluid. 5 In each case only a single sheet of aber-
May I , 1985 Am J Obstel Gynecol
Fig. 2. Real-time scans display an aberrant sheet of tissue with a free edge within the amniotic fluid (Case 9) . This pregnancy resulted in a normal infant. A, Although fetal parts (H = head, E = extremity) bridge the sheet of tissue (open arrow), there was no fetal deformity, edema, or restriction of motion. Note the broad base of the aberrant sheet of tissue (small closed arrow) . B, This scan plane sections longitudinally through the thickened free edge of the sheet of tissue (closed arrow) (H = head). C, In this plane of section, which images the aberrant sheet of tissue transversely, the sheet of tissue appears band like (open arrow). Again noted is its bulbous free edge (closed arrow) as well as the bridging fetal pans (H = head, E = extremity) . rant tissue was visible. In two insta nces a sheet of tissue that had been seen earlier in pregnancy was no longer visible later in pregnancy. Although the sheet of tissue touched five of the fetuses, in none did it appear attached to the fetus; the fetus was able to alter its position relative to the sheet of tissue. Similarly, although fetal
Amniotic band syndrome 65
Volume 152 Number I
Table I. Sonographic and follow-up data regarding the six cases in which diagnosis of amniotic band syndrome was made on basis of antenatal sonogram (case 2 has been reported previously3)
Case No.
Reason for sonography
Attached to or Menstrual Sheet or Single or touching Bridging age (wk) bands multiple fetus fetal parts
Associated edema, deformity
Amniotic sheet or bands associated with fetal deformity I Twins; anom21 Bands Multiple Attached Numerous Multiple facial clefts aly on outside sonogram (?) 21 Sheet Single Attached Numerous Asymmetric 2 Maternal edema drug abuse Fetal deformities in nonembryonic distributions; aberrant sheets or bands not visualized 3 Omphalocele 37 One leg on outside absent sonogram 4 Abnormalities on outside sonogram
25
5 Anomalies
22
6 Omphalocele on outside sonogram (?)
30
on outside sonogram (?)
parts intermittently bridged the aberrant sheet of tissue in three instances, in no case was there associated fetal deformity or restriction of motion. Each pregnancy resulted in an infant without evidence of the amniotic band syndrome. In Case 12, sonography also demonstrated evidence of alobar holoprosencephaly, a developmental anomaly not related to the amniotic band syndrome. Comment
Most contemporary authors concur with the hypothesis elaborated by Torpin 6 in 1968, which explains the characteristic clinical features of the amniotic band syndrome. I. ' ·5 . 7· 10 Torpin asserted that rupture of the amnion leads to subsequent entanglement of various embryonic or fetal parts by fibrous mesodermic bands that emanate from the chorionic side of the amnion. Entrapment of fetal parts by the bands may cause lymphedema, amputation, or slash defects in nonembryologic distributions. Torpin further suggested that the amnion, which is contiguous with the fetal skin at the umbilicus, protects the fetus from contact with the chorion. When disruption of the amnion occurs, the fetus may
One leg absent
Restriction of motion Other deformities Yes
Yes
Asymmetric encephalocele
Follow-up Amniotic band syndrome (autopsy)
No
Amniotic band syndrome (autopsy)
Gastroschisis with exteriorization of liver and bowel Gastropleu ral schisis with exteriorization of liver, bowel, and heart Gastropleu ral schisis with exteriorization of liver and heart, asymmetric encephalocele Gastroschisis with exteriorization of liver and bowel, marked scoliosis, small thorax
Amniotic band syndrome (autopsy) Amniotic band syndrome (autopsy) Amniotic band syndrome (autopsy)
Amniotic band syndrome (autopsy)
adhere to and fuse with the chorion with subsequent maldevelopment of the subjacent fetal tissue. Although the amniotic band syndrome manifests variable patterns of deformity, a proclivity for certain anomalies typifies the disorder and permits prenatal diagnosis. For example, exteriorization of the liver rarely occurs with gastroschisis. II. 12 However, in each of our four fetuses who had gastroschisis associated with the amniotic band syndrome, hepatic exteriorization occurred. This suggests that when gastroschisis results in exteriorization of the liver the amniotic band syndrome should be strongly considered. Similarly, approximately 90% of encephaloceles occur in the midline because of failure of neural tube fusion. 13 In both of our fetuses with an encephalocele associated with the amniotic band syndrome the encephalocele occurred laterally. Therefore, identification of an asymmetric encephalocele should strongly suggest the amniotic band syndrome, although asymmetric encephaloceles can occur without amniotic band syndrome. Other craniofacial malformations such as asymmetric anencephaly and bizarre clefting patterns should also suggest the amniotic band syndrome. Cleft
66
Mahony et al.
May I, 1985 Am J Obstet Gynecol
Fig. 3. Representative sonograms of a fetus (Case I) with the amniotic band syndrome. A, Scan through the fetal head demonstrates an asymmetrical encephalocele (solid arrows) (F = falx cerebri). S, Numerous bands (arrows) are attached to the fetal extremities (E) and restrict fetal motion. Other scans showed facial clefts in a nonembryologic distribution. These features enabled an antenatal diagnosis of the amniotic band syndrome.
ion
Amnio~I---+---j
,H---!-IPalrti(JI uterine septation
Fig. 4. Schematic drawing of the gravid uterus. Amnion and chorion extend over a uterine synechia or partial septation. This creates a sheet of aberrant tissue with a free edge within the amniotic fluid. Despite the "free" edge, the amnion is not disrupted. Although fetal parts may bridge or touch the aberrant sheet of tissue, there is no associated fetal deformity or restriction of motion. This appearance is not associated with the amniotic band syndrome.
lip and palate are common paramedian or median malformations that occur in characteristic patterns caused by failure of fusion of the paraxial mesodermic masses. 14 Although they may occur in association with other congenital anomalies, there is no reported in-
creased incidence with asymmetric encephaloceles, gastropleural schisis, or multiple amputations. On the other hand, facial fissures associated with the amniotic band syndrome form in bizarre, nonembryologic patterns.
Amniotic band syndrome 67
Volume 152 Number I
Table II. Sonographic and follow-up data regarding the seven cases in which an aberrant sheet of tissue with a free edge in the amniotic fluid was present but there were no associated fetal deformities Attached to Associated edema, Restriction Single or or touching Bridging f etal parts deformity of motion fetus multiple
Other deformities
Follow-up
None
None
Normal infant
None None
None None
None None
Normal infant
None None
None None
None None
None None
Normal infant
Leg
None
None
None
None
None
None
None
None
None
None
None
Normal infant
None
None
None
Normal infant
None
None
None
Normal infant
None
None None None
None None None
None
None
None
Reason for sonogram
Menstrual age (wk)
Sheet or bands
7
Size-dates discrepancy
13
Sheet
Single
Touching fetus
None
None
8
Previous holoprosencephaly
21 19
Not visible Sheet
Single
Extremity, trunk
Head
9
Maternal age (35 yr)
25, 29, 38 17
Sheet Sheet
Single Single
Neither Neither
20
Sheet
Single
23-33 (every 2-5 wk) 34
Sheet
Single
Touching neck Neither
Sheet
Single
Neither
17
Sheet
Single
Neither
23
Sheet
Single
25, 29 32 29
Sheet Not visible Sheet
Single Single
Touching occiput
20
Sheet
Single
Neither
Case No.
10 II
Previous fetal death Size-dates discrepancy
12
Maternal diabetes
13
Amniotic band on outside sonogram
Umbilical cord Touching None legs, trunk Neither None
None None Stillborn at 30 Alobar menstrual holoprosencephaly weeks with alobar holoprosencephaly, otherwise normal Normal None
(?)
Although extremity amputations may result from genetic or teratogenic causes, several distinguishing features permit identification of amputations related to the amniotic band syndrome.6 Whereas genetic or teratogenic amputations tend to be bilaterally symmetrical, amputations caused by the amniotic band syndrome are usually asymmetric. While syndactyly that involves the base of the digits implies genetic or teratogenic causes, syndactylism that originates distally suggests the amniotic band syndrome. Identification of a fibrous band of tissue within a constricting ring with distal elephantiasis or protrusion of uncovered bone distal to the soft tissue at the site of amputation constitute pathognomonic signs of the amniotic band syndrome. Such fibrous bands also can be found when facial fissures are caused by this syndrome. Constriction of the umbilical cord by an amniotic band represents potential "amputation" at its most extreme. Among 36 fetuses with umbilical cord constriction identified by Torpin,6 none survived.
When antenatal sonography visualizes an aberrant sheet or bands of tissue attached to a fetus with characteristic deformities and restriction of motion , a diagnosis of the amniotic band syndrome can be made. Even when the aberrant sheets or bands are not visualized, characteristic fetal deformities in nonembryologic distributions provide evidence highly suggestive of the amniotic band syndrome. Such information will alert the perinatalogist and geneticist to obtain a detailed postnatal examination. On confirmation of the diagnosis, appropriate counseling can be performed. The recurrence risk for the aberrant bands and any consequences thereof appear to be negligible. 1O Aberrant sheets of tissue with a free edge within the amniotic fluid often occur in the absence of the amniotic band syndrome. During Torpin's" extensive review of 400 fetuses with amnion rupture, he discovered only three cases in which the fetus escaped injury. In contrast, all seven of the pregnancies in the current study in which we visualized a single aberrant sheet of tissue
68 Mahony et al.
within the amniotic fluid but no associated fetal deformity resulted in infants without the amniotic band syndrome. The sonographically visible aberrant tissue within the amniotic fluid in these cases may represent intact amnion and chorion extending over a partial uterine septation or synechia (Fig. 4). That the base or free edge of the aberrant sheet of tissue often appeared disproportionately thickened supports this hypothesis. Furthermore, we are aware of an additional case with similar findings in a woman with uterine synechia documented by hysterosalpingography (Rich P, personal communication). Finally, in two instances the aberrant sheet disappeared as the uterus enlarged. Possible explanations of this sequence are that a synechia was stretched beyond its tensile strength, permitting rupture and disappearance of the observed abnormality, or that the sheet was simply compressed against the uterus by growth of the fetus and thus became imperceptible. In the above-described seven cases there would be no chance for fetal entanglement and only a very small chance for entrapment of fetal parts. Therefore antenatal sonographic demonstration of a sheet of aberrant tissue in the amniotic fluid surrounding a fetus without evidence of associated deformity does not imply the presence of the amniotic band syndrome. This finding alone does not constitute sufficient indication for elective pregnancy termination. REFERENCES I. Seeds JW, Cefalo RC, Herbert WNP. Amniotic band syndrome. AM J OBSTET GVNECOL 1982; 144:243.
May I, 1985 Am J Obstet C ynecol
2. OssipoffV, Hall BD. Etiologic factors in the amniotic band syndrome: a study of twenty-four patients. Birth Defects 1977;13:117. 3. Fiske CE, Filly RA, Golbus MS. Prenatal ultrasound diagnosis of amniotic band syndrome. J Ultrasound Med 1982;1:45. 4. Worthen NJ, Lawrence D, Bustillo M. Amniotic band syndrome: antepartum ultrasonic diagnosis of discordant anencephaly. JCU 1980;8:453. 5. Burrows PE, Lyons EA, Phillips HJ , et al. Intrauterine membranes : Sonographic findings and clinical significance. JCU 1982;10:1. 6. Torpin R. Fetal malformations caused by amnion rupture during gestation. Springfield, Illinois: Charles C Thomas, 1968:1-76. 7. Rushton DI. Amniotic band syndrome. Br Med J 1983; 286:919. 8. Moessinger AC, Blanc WA, Byrne J , et al: Amniotic band syndrome associated with amniocentesis. AM J OBSTET GVNECOL 1981;141 :588. 9. Miller ME, Graham JM , Higginbottom MC, et at. Compression-related defects from early amnion rupture: evidence for mechanical teratogenesis. J Pediatr 1981 ;98: 292. 10. Higginbottom MC,Jones KL, Hall BD, et at. The amniotic band disruption complex : timing of amniotic rupture and variable spectra of consequent defects. J Pediatr 1979;95: 544. II . Nakayama DK. Management of the fetus with an abdominal wall defect. In: Harrison MR, Golbus MS, Filly RA, eds. The unborn patient: prenatal diagnosis and treatment. Orlando: Grune & Stratton Inc. , 1984:217-34. 12. Raffensperger JG. Gastroschisis. In : Nyhus LM, Condon RE, eds. Hernia, ed 2. Philadelphia: J B Lippincott, 1978:357-61. 13. Fink Ij, ChiDn DH, Callen pw. A potential pitfall in the ultrasonographic diagnosis of fetal encephalocele. J Ultrasound Med 1983;2:31 3. 14. LongacreJ]. Cleft palate d eformation : causation and prevention. Springfield, Illinois : Charles C Thomas, 1970: 104.