Amniotic Band Sequence

A set of congenital anomalies caused by disruption, deformation and, at times, secondary malformation, associated with fibrous strands of amniotic origin that constrict, amputate or tether parts of the embryo, the fetus or the umbilical cord; sporadic and without an established causal gene, it is distinguished from the limb–body wall complex and from genetic phenocopies such as Adams-Oliver syndrome.

Literature and regulatory information updated: 29 October 2026.

0. Initial Reference Table

1. Introduction

1.1. Historical descriptions

The relationship between strands of amniotic membrane and structural defects of the fetus was recorded by Paul Portal in 1685, in La Pratique des Accouchements, but the full spectrum of lesions was only systematised in 1965, when Richard Torpin described amniochorionic mesoblastic fibrous strings and amniotic bands as a cause of constrictive malformations and fetal death [10, 30]. Torpin developed the idea in a 1968 monograph on fetal malformations caused by rupture of the amnion during gestation, and his proposal came to be called the extrinsic theory [8, 10]. Before him, George Streeter had argued, in 1930, for an intrinsic theory: the anomalies and the rings themselves would result from defective development of the germ disc, without mechanical involvement of amniotic strands, which is why one of the synonyms of the entity is "Streeter dysplasia" [1, 8].

1.2. Nomenclature

The term "syndrome" has been replaced, in much of the dysmorphology literature, by "sequence", because the anomalies arise from a cascade triggered by an initial insult that may have more than one cause, and not from a single aetiology with a fixed pattern [2, 31]. Several synonyms coexist: amnion rupture sequence, ADAM sequence (amniotic deformity, adhesion, mutilation), amniotic disruption complex, congenital constriction band or ring syndrome and Streeter dysplasia [1, 2]. Orphanet classifies the entity as a malformation syndrome (ORPHA:295000), with a definition centred on fibrous, circumferential, partial or complete constriction rings, with a predilection for the limbs and an expression ranging from a skin indentation to amputation of fetal segments [1]. The former grouping ORPHA:1034 ("Amniotic bands") is marked as obsolete [1]. In OMIM, entry 217100 is titled "Constricting bands, congenital", with the synonyms amniotic band sequence and Streeter anomaly, and includes the ADAM complex, terminal transverse defects of the arm and congenital amputation [14]. The designation "ADAM complex" was given by John Opitz to the association of constriction bands with cleft lip and palate and other facial malformations, described by Keller and colleagues in 1978 in two related boys [14].

1.3. Separation from the limb–body wall complex

For decades, thoraco- and abdominoschisis, exencephaly and encephalocele associated with amniotic adhesions were included in the same sequence. Van Allen and colleagues (1992) also showed that vascular disruption due to death of a co-twin or to embolic infarcts in utero can cause terminal reduction defects and constriction rings similar to those of ABS without abnormal amnion [14]. The pathology studies of Van Allen and colleagues (1987) in 25 fetuses established criteria for the limb–body wall complex (LBWC), defined by the presence of at least two of three findings: exencephaly or encephalocele with facial clefts, thoraco- and/or abdominoschisis, and limb defect [23]. The demonstration of intact amnion in some cases, of internal anomalies in 95% and of persistence of the extraembryonic coelom led Smith's Recognizable Patterns of Human Malformation to describe the inclusion of LBWC in the amnion rupture sequence as "incorrect" and to treat it as a pattern of different pathogenesis [10, 11, 23]. Martínez-Frías (1997) showed, with data from the Spanish ECEMC registry (Spanish Collaborative Study of Congenital Malformations), that the two entities also separate epidemiologically, and Russo and colleagues (1993) distinguished two phenotypes within LBWC [31, 32]. The boundary remains debated: the European surveillance network EUROCAT (European Surveillance of Congenital Anomalies) considers that the two entities have an overlapping phenotype and unknown aetiology, and classifies cases with LBWC and bands as LBWC [8].

1.4. First fetal intervention

In 1997, Quintero and colleagues, in Tampa, released by fetoscopy bands constricting the limbs in two fetuses, with preservation of distal flow and function; this was the first prenatal surgical intervention for constrictive bands and the first fetal surgery directed at a non-lethal entity [33]. It was preceded by ovine models of fetoscopic release (1995) and followed by lamb amputation models and clinical series [26].

1.5. Definition and scope of the article

Amniotic band sequence (ABS) designates the set of anomalies due to constriction, amputation, adhesion or tethering attributable to strands of amniotic origin in a fetus with no other identified cause, with predominance of the limbs and possible involvement of the skull, face, body wall and umbilical cord [2, 10]. LBWC is treated as a borderline entity, with its own criteria, because it shares bands and adhesions but has internal anomalies and a lethal prognosis [8, 11]. Adams-Oliver syndrome, which can be a complete phenocopy of ABS, limb reduction defects of genetic cause and the Poland sequence enter the differential diagnosis [13, 34].

2. Molecular Genetics and Pathophysiology

2.1. State of aetiological knowledge

ABS has no established causal gene and is not considered hereditary [2, 10]. In the rare cases with a karyotype, chromosome studies were normal, and the published familial occurrences are few and, in part, poorly documented or misdiagnosed [2, 35]. Temtamy and McKusick (1978) found no clear or simple genetic basis [14]. Candidate genes without confirmation have been proposed: a human homologue of the mouse disorganization gene for ABS, IQCK, and heterotaxy or caudal development genes for LBWC [4, 8]. The aetiology is probably heterogeneous, with more than one mechanism operating in subgroups of patients [8]. Isidor and colleagues and Purandare and colleagues (2009) described patients with severe limb anomalies initially diagnosed as ABS who also had hamartomatous skin pedicles, and proposed that this "ABS plus" corresponds to a phenotype similar to that of the mouse disorganization mutant [14]. Maas and colleagues (2009) described two women with Goltz-Gorlin syndrome (X-linked focal dermal hypoplasia) with female fetuses with a phenotype similar to LBWC or to the pentalogy of Cantrell, suggesting that some of these diagnoses correspond to fetuses severely affected by that syndrome [14].

2.2. Extrinsic theory (amnion rupture)

According to Torpin's theory, early rupture of the amnion exposes the embryo or fetus to the chorionic surface, where mesodermal filaments form and entangle developing parts, especially the limbs [10, 26]. Before 12 weeks, the amnion and chorion are completely separate membranes, which has been proposed as a vulnerability factor and explains why rupture probably occurs in that period, although band disruption can happen at any stage of gestation [10]. Constriction causes ischaemia of the distal segment, oedema and, with progression, loss of function and amputation [26]. The theory explains atypical orofacial clefts, pseudosyndactyly, amputations and wall defects, but not the internal organ anomalies that characterise LBWC [8]. Some cases have a known or presumed traumatic cause, such as two attempts at early termination of pregnancy with an object introduced into the uterus and a fall from a horse during pregnancy [10].

2.3. Intrinsic theory and vascular theory

Streeter's intrinsic theory attributes the anomalies to a primary defect of the germ disc [8]. Van Allen and colleagues proposed an alteration of the embryonic blood supply between the 4th and 6th weeks, with disruption of already formed tissues, persistence of embryonic structures and secondary malformations; persistence of the extraembryonic coelom would allow rupture of an unsupported amnion and the formation of rings, tags and adhesions [11, 23]. In the 25 fetuses with LBWC they studied, limb defects resulted from disruption of embryonic vessels in 84%, from amniotic bands or adhesions in 16% and from deformation or haemorrhage in the clubfeet (44%), with distoproximal progression in 92% and no concordance of side (p = 1.0) or region (p = 0.18) with the wall defect [36]. The Oxford Desk Reference records the two hypotheses for transverse defects due to bands: fibrous strings of amniotic origin that constrict or cleave normal development, or a primary alteration of fetal blood flow, with the bands as a secondary phenomenon [34].

2.4. Other hypotheses

Hartwig and colleagues related the defects to malfunction of the ectodermal placodes of the body wall, with mesoderm deficiency and disturbance of embryonic folding; Hunter, Seaver and Stevenson (2011) placed the origin of the ventral wall complex at the embryonic disc stage, owing to ectodermal deficiency, with some of the associated anomalies as secondary complications [11, 37]. Vitelline vascular "steal" (Stevenson, 2021) and NAD+ deficiency (nicotinamide adenine dinucleotide; Mark, 2022) have also been proposed [8]. LBWC is grouped with the recurrent constellations of embryonic malformations (pentalogy of Cantrell; OEIS complex, of omphalocele, exstrophy, imperforate anus and spinal defects; VACTERL association, of vertebral defects, anal atresia, cardiac defects, tracheo-oesophageal fistula, renal and limb anomalies; oculoauriculovertebral spectrum; and MURCS, of Müllerian aplasia, renal dysplasia and cervical somite anomalies), with early embryonic origin, rare familial recurrence and an excess of discordant monozygotic twins [4, 8].

2.5. Risk factors

Risk factor studies have produced inconsistent results, and no factor has been found reproducibly [8, 35]. The most studied are summarised in the following table.

The EUROCAT review also lists, without consistency between studies, unplanned pregnancy, bleeding and fever in the 1st trimester, pregestational diabetes, smoking, alcohol, aspirin, misoprostol, bronchodilators, high altitude, amniocentesis and chorionic villus sampling [8]. First-trimester bleeding is associated with a 15-fold higher prevalence of limb reduction defects, and chorionic villus sampling, dilatation and curettage, misoprostol and phenytoin produce defects through vascular disruption of previously normal limbs [34].

2.6. Post-procedure bands

Post-procedure band disruption sequence is the iatrogenic form of the entity. In the Leiden series of 672 pregnancies with twin–twin transfusion syndrome treated by fetoscopic laser, it occurred in 2.2% (15/672), in recipients (67%) and donors (33%), mainly affected the lower limbs (73%) and caused toe amputation in 5/15 and fetal death from cord constriction in 1/15 [41]. Lower gestational age at laser (OR 1.43 per week; 95% CI 1.12–1.79) and post-procedure chorioamniotic separation (OR 41.66; CI 5.44–319.25) were independent factors [41]. Cases have been described after amniocentesis and placement of a thoracoamniotic shunt, and 4 of the 37 cases operated on by fetoscopy in the 2024 systematic review had arisen after amniocentesis [2, 26].

2.7. Genetic predisposition of connective tissue

Callaghan and colleagues described two paternal half-siblings with ABS whose father, after a severe vascular event, was diagnosed with vascular Ehlers-Danlos syndrome due to a de novo pathogenic variant in COL3A1; the variant was present in both affected children and absent in an unaffected child [7]. Because the amnion derives from fetal tissue and contains type III collagen, the authors propose that reduced production of this collagen makes the membrane fragile, and recommend considering vascular Ehlers-Danlos syndrome in the presence of ABS [7]. The same authors report familial ABS in children of mothers with connective tissue disorders [7]. These reports do not change the classification of ABS as sporadic, but identify a subgroup in which the family history has medical consequences.

2.8. Mechanisms of the manifestations

The primary lesions are disruptions: constriction rings, intrauterine amputations, pseudosyndactyly and umbilical cord constriction [10]. To these are added deformations due to tethering of a limb, which reduces fetal movements (scoliosis, foot deformities), or due to constraint linked to loss of amniotic fluid; oedema, haemorrhage and resorption necrosis may occur [10]. Because the insult is external, internal organs are almost never affected, and no two fetuses have the same set of findings [10]. Severity depends on the position of the bands: thin peripheral strands cause defects of the extremities, whereas broad bands crossing the cavity can cause complex wall defects [2]. The timeline of limb development helps to date the insult: the upper limb buds appear at about 27 days after fertilisation (5 weeks and 6 days of gestation) and the lower ones at 28–30 days; the fingers begin to separate at 38–40 days and are fully separated at 52–53 days (9 weeks and 3–4 days), and the toes at 54–55 days [34].

3. Clinical Spectrum and Manifestations by System

3.1. General principles of the phenotype

The spectrum ranges from an isolated skin indentation to multiple amputations, extensive craniofacial defects and fetal death from cord constriction [1, 2]. The most frequent phenotype is a constriction ring or a limb amputation in an otherwise normal child [10]. The defects are typically asymmetric and, when more than one limb is involved, the distribution is uneven; a symmetric pattern or regular involvement of several limbs should prompt consideration of an underlying genetic disorder [2, 34]. Pape and Gorla group the clinical presentation into four main categories: constriction bands, limb defects, neural tube defects and craniofacial defects [2].

3.2. Reference cohorts

The largest series is that of the EUROCAT network, with 866 cases of ABS and 451 of LBWC recorded in 30 registries from 15 European countries between 1980 and 2019, including live births, stillbirths and terminations of pregnancy for medical reasons (TOPFA) [8]. In the analysis of the spectrum, after excluding cases with another syndrome or without a recorded major anomaly, 735 ABS and 297 LBWC remained [8]. The following table compares the frequencies of anomalies in ABS with other population series cited in the same publication.

Source: Bergman et al. 2023, table 3, which compiles Orioli 2003, Martínez-Frías 2000, Koskimies 2015 and Evans 1994 [8]. CL±P: cleft lip with or without cleft palate; CP: cleft palate; CAKUT: congenital anomalies of the kidney and urinary tract. Inclusion criteria differ between series (for example, the Hungarian series included only reduction defects due to bands), which explains part of the variation. Cases excluded because of another syndrome included trisomy 18 (5), trisomy 21 (3), trisomy 13 (3), other genetic or chromosomal disorders (8) and other conditions (6, including congenital cytomegalovirus, twin–twin transfusion syndrome, pentalogy of Cantrell and caudal regression) [8].

In the Alberta Congenital Anomalies Surveillance System (Canada), 153 cases of bands and wall defects were recorded between 1980 and 2012 among 1,411,652 live births and stillbirths (1.08/10,000), with 52% male, mean maternal age of 27 years, mean weight of 2701 g and mean gestational age of 35 weeks [35]. Limb deficiency was present in 78%; the most common phenotype was bands with limb deficiency (48%), digital deficiency was the most frequent type (56%), the upper limbs alone were affected in 44% and there was no side preference; cases with a wall defect had more severe limb deficiencies [35]. In a Mexican series of 50 cases with prenatal diagnosis (1993–2010), craniofacial defects predominated (78%; mainly encephalocele and facial clefts), followed by defects of the extremities (70%) and defects of the abdominal wall, spine or thorax (52%), a profile of more severe prenatal cases than that of live-birth series [42].

3.3. Limbs

Constriction rings may arise in any segment and range from a superficial groove to a deep constriction with distal lymphoedema; intrauterine amputation may affect phalanges, whole digits, the hand, the foot or a limb; there is a predilection for the upper limbs and for distal segments [1, 10, 43]. Pseudosyndactyly, contractures, fractures and club foot or club hand complete the picture [2]. Smith illustrates digital amputations by amnion strands, ankle constrictions with deformation and amputation, and pseudosyndactyly with disruption of digital morphogenesis [10]. Al-Qattan classified 31 upper limbs with ring amputations in 20 patients: type I, proximal amputation (1 limb); type II, digital amputation with coning or overlapping of digits (20 hands), subdivided according to whether all digits, the ulnar, the radial or the central digits are involved; type III, without coning (10 limbs), with IIIA for several digits and IIIB for a single one [44]. Talipes equinovarus is frequent, with values of 11–22% in population series and up to 50% in orthopaedic series [8, 28]. Compressive nerve lesions may coexist, such as complete ulnar nerve palsies diagnosed soon after birth from the intrinsic-minus posture of the hand and the inability to actively extend the proximal interphalangeal joints [45]. Weinzweig described gangrene of an extremity due to a congenital band as the result of intrauterine or postnatal vascular compromise, often completed in utero with healing or amputation, and introduced an intermediate stage (3B) of severe lymphatic–venous compromise with soft-tissue loss [46].

3.4. Skull, face and eyes

Craniofacial defects include encephalocele, anencephaly, facial clefts, cleft lip and palate, orbital involvement and meningocele, usually asymmetric and outside the suture lines or the lines of closure of the facial processes [2]. Ocular involvement is frequent when the face is affected, with microphthalmia, hypertelorism, ptosis, corneal opacities, eyelid colobomas and lacrimal duct obstruction [2]. In EUROCAT, neural tube defects were present in 19.0% of ABS, mainly anencephaly and encephalocele, and orofacial clefts in 9.8% [8].

3.5. Body wall and spine

In ABS, ectopia cordis, rib clefts, intestinal extrusion, omphalocele and bladder exstrophy may occur, as well as spinal defects and scoliosis [2]. In EUROCAT, 12.2% of ABS had an abdominal or thoracic wall defect [8]. Scoliosis and foot deformities may result from reduced fetal movements due to tethering [10].

3.6. Umbilical cord

Bands involve the cord in about 10% of cases and are a known cause of fetal death [47]. In the systematic review of cases operated on by fetoscopy, the cord was involved in 24.3% (9/37), and in 5 of those 9 the involvement was only seen during fetoscopy [26]. In a series cited by Pape and Gorla, 4 of 5 stillbirths with ABS had cord involvement [2].

3.7. Internal organs

Because the disruption is external, internal anomalies almost never occur and surface examination usually shows all the anomalies [10]. In EUROCAT, congenital heart disease (5.3%) and respiratory (1.4%), gastrointestinal (3.3%), renal (2.0%) and genital (1.9%) anomalies were infrequent in ABS, in contrast with LBWC [8].

3.8. Perinatal consequences

Among the live births with ABS in EUROCAT, 37.8% were born before 37 weeks, with a mean weight of 1847 g below 37 weeks and 3175 g between 37 and 41 weeks, and survival to the first week was 94% (381/406) [8]. When there has been chronic loss of amniotic fluid, the newborn may present the oligohydramnios deformation sequence, with incomplete lung development and respiratory failure [10]. There is an increased risk of premature rupture of membranes (PROM), preterm birth and low birth weight, compounded by wall defects [2].

3.9. Limb–body wall complex

LBWC combines thoraco- or abdominoschisis with evisceration into a persistent extraembryonic coelom, limb defects and, frequently, exencephaly or encephalocele with facial clefts [11]. The amnion is continuous with the skin at the edge of the defect and the cord is short and partly devoid of amniotic covering [11]. Limb defects due to rings occur occasionally, but those that bands do not explain are more frequent: a single bone of the forearm or leg, ectrodactyly, radioulnar synostosis and polydactyly [11]. Encephaloceles are usually anterior, often multiple and sometimes adherent to the amnion, and the facial clefts do not follow the lines of closure, with disruption of the frontonasal processes [11]. Internal anomalies are frequent: cardiac, pulmonary (lobation defects), absent diaphragm, non-rotation, intestinal atresia or shortening, gallbladder anomalies, renal agenesis, hydronephrosis or dysplasia, genital anomalies (abnormal external genitalia or uterus, absent gonad, streak ovaries, bladder exstrophy), persistent left superior vena cava, myelomeningocele, polysplenia and hypoplastic sacrum [11].

Sources: Bergman et al. 2023, table 4; Thomas et al. 2025 [4, 8]. Earlier series, smaller and not population-based, described higher frequencies (for example, neural tube defects in 42.6% and orofacial clefts in 51.9% in Bamforth's review of 54 cases; anorectal atresia in 56.3% and renal agenesis in 62.5% in a Danish series of 16 cases), which reflects selection of more severe cases [8]. In Van Allen's series, 95% (24/25) of the fetuses had internal anomalies, 72% of them attributable to vascular disruption, and 40% had amniotic tags and adhesions in other locations, with no difference in internal anomalies between fetuses with and without bands [23]. In LBWC, 89.2% of the live births in EUROCAT were born preterm and survival to the first week was 5% (2/37) [8].

4. Clinical Recognition and Warning Signs

4.1. When to suspect it in the prenatal period

ABS should be considered in the presence of hyperechogenic linear membranes attached to the fetus, constriction rings with distal oedema, amputations, a fixed fetal position that does not change when the pregnant woman moves, and cranial, facial or wall defects of unusual and asymmetric location, especially if they coexist with limb lesions [2]. The lesions can be seen from the 1st trimester [2]. In EUROCAT, prenatal detection of ABS rose from 17.9% in 1980–1989 to about 60% from 2000 onwards, whereas that of LBWC was consistently above 90% (98.8% in 2010–2019) [8]. The context also guides suspicion: twin pregnancy, intrauterine procedures, early fetoscopic laser, chorioamniotic separation and previous uterine surgery [8, 40, 41].

4.2. When to suspect it in the newborn

In the newborn, ABS is suggested by visible constrictions, amputations and non-midline craniofacial or wall defects of unusual location; in these cases the fresh placenta and membranes should be examined for bands [2, 10]. There may be a clear history of tight fibrous strings around digits at the time of delivery [34]. ABS should also be considered in a stillbirth, especially if there is cord constriction [2].

4.3. Warning signs of another diagnosis

Some findings should rule out the hypothesis of isolated ABS or prompt a genetic assessment: symmetric defects or defects in several limbs; a scalp defect at the vertex, which suggests Adams-Oliver syndrome; a family history of limb or scalp defects; internal organ anomalies; longitudinal defects (for example, radial aplasia), which do not belong to the band spectrum; palsies of cranial nerves VI and VII; an anomaly of pectoralis major; macrocytic anaemia [13, 34]. A family history of vascular rupture, arterial dissection or connective tissue fragility should prompt consideration of vascular Ehlers-Danlos syndrome in one of the parents [7].

4.4. Urgent signs

In the fetus, the urgent situations are involvement of the umbilical cord (risk of fetal death within days to weeks according to the experience of the Mannheim centre) and constriction of a limb with abnormal but still present distal Doppler, which is the window in which release can save the segment [48, 49]. In the newborn, deep constriction with progressive lymphoedema, cyanosis, soft-tissue necrosis or absent distal pulses constitutes vascular compromise that may require urgent surgical release [2, 46]. A complete nerve palsy distal to a band is also an indication for release as early as possible [45]. The newborn with pulmonary hypoplasia due to oligohydramnios should receive full ventilatory support, because lung morphogenesis continues and the prognosis may be excellent [10].

4.5. Screening

There is no newborn screening. The second-trimester anomaly scan and the first-trimester ultrasound are the moments of detection; maternal serum alpha-fetoprotein is usually markedly raised in the body wall complex [8, 12].

5. Diagnosis: Criteria, Tests and Algorithms

5.1. Diagnostic criteria

There are no consensus diagnostic criteria for ABS or for LBWC, which explains part of the variation in prevalence estimates between studies [8]. In practice, the diagnosis of ABS rests on three elements: lesions compatible with constriction or amputation of asymmetric distribution; physical evidence of amniotic disruption (bands seen on ultrasound, band tissue adherent to the newborn, torn, rolled or knotted amnion on placental analysis); and absence of another explanation [10, 13]. Smith considers examination of the placenta and membranes diagnostic, as it shows aberrant amnion strands or rolled amnion remnants at the placental base of the cord [10]. Some clinicians accept the diagnosis only with physical evidence of bands, and, without it, constriction rings may be interpreted as a sign of vascular disruption [13].

For LBWC, the Van Allen criteria (1987) require two of three findings: exencephaly or encephalocele with facial clefts; thoraco- and/or abdominoschisis; and limb defect [23]. Martínez-Frías proposed restricting the designation "body wall complex" to cases with an abdominal wall defect with evisceration (excluding omphalocele and including gastroschisis) associated with other anomalies, and excluding from LBWC the child with encephalocele, facial cleft and limb defect without a wall defect [4]. Body stalk anomaly has its own prenatal criteria (Goldstein, 1989): wall defect, skeletal anomalies such as severe scoliosis, and an absent or very rudimentary cord [4]. On the basis of 51 population-based cases from Alberta, Thomas and colleagues (2025) proposed adapting the criteria to prenatal imaging: accepting any wall defect, whether called abdominoschisis, atypical omphalocele or gastroschisis, when accompanied by other features; removing facial cleft as a requirement alongside exencephaly or encephalocele; and adding short cord (41.2% of cases) and severe scoliosis or kyphoscoliosis (76.5%; detected prenatally in 45.1%) as supporting findings [4].

5.2. Prenatal ultrasound

When there is suspicion, the pregnant woman should be referred to maternal–fetal medicine for a detailed anomaly scan with a targeted search for bands [2]. Bands appear as thin, linear, hyperechogenic structures, without flow on colour Doppler; moving the pregnant woman during the examination may reveal a fixed fetal position suggesting tethering [2]. When a constriction progresses to amputation, a small distal remnant remains, the "vestige sign", described in an Israeli series in amputations after 15 weeks [2, 40]. In all suspected extremities, colour Doppler should assess perfusion proximal to, at the level of and distal to the constriction [2]. Ferrer-Marquez and colleagues recommend comparing the Doppler proximal and distal to the band with that of the contralateral limb and measuring the circumferences of both limbs to quantify the progression of oedema [26]. The cord should be examined carefully, but its involvement is difficult to demonstrate before surgery: in 5 of 9 cases with cord involvement in the systematic review, only fetoscopy showed it [26, 50].

5.3. Hüsler prenatal classification

Hüsler and colleagues (2009) proposed a staging classification based on ultrasound and Doppler of the extremities, to correlate prenatal findings with outcome and to select candidates for fetal surgery [49]. The stages, as reproduced in secondary sources, are shown in the following table [2, 51].

The authors concluded that abnormal but present distal Doppler flow identifies the cases most suitable for surgery [49]. The classification has not been validated and does not address cord involvement [26]. Riehle and colleagues add a functional criterion: arterial and venous flow present with active distal movements indicate a salvageable segment, whereas isolated poor arterial flow and absence of movements indicate loss of the segment [48].

5.4. Fetal magnetic resonance imaging

Fetal magnetic resonance imaging is a complement in complex cases or when release is being considered, but ultrasound has a higher detection rate for bands [2].

5.5. Morphological classifications

Guzmán-Huerta and colleagues proposed, from 50 prenatal cases, four phenotypic groups: I, craniofacial defect with limb defects; II, craniofacial, limb and abdominal wall, spine and/or thorax defects; III, limb defect with abdominal wall, spine and/or thorax defect; IV, isolated defect (craniofacial, limb or thoracoabdominal) [42]. For limb defects, the EUROCAT classification distinguishes terminal transverse defects (absence of distal structures with almost normal proximal segments, from a nail or phalanx to a whole limb), proximal intercalary defects, longitudinal defects (absence or severe hypoplasia of the lateral part of the limb), split hand or foot and defects of multiple types; soft-tissue rudiments at the end of a proximal transverse defect only lead to an intercalary classification if there are significant skeletal elements [34]. The defects of ABS are, in the great majority, terminal transverse [34]. For upper limb amputations due to rings, the Al-Qattan classification (types I to III) is used, and for vascular compromise of the foot, the revised Weinzweig classification with the intermediate stage 3B [44, 46]. In LBWC, Russo and colleagues distinguished one phenotype with craniofacial defects and bands or adhesions (attributed to early vascular disruption) and another without craniofacial defects, with urogenital anomalies, anal atresia, abdominal placental insertion and persistence of the extraembryonic coelom (attributed to intrinsic embryonic malformation) [32]; in Chinese ultrasound series of 37 fetuses, 4 were type I, 31 type II and 2 had features of both [52]. Thomas and colleagues, in Alberta, interpret these phenotypes as a spectrum, with the location of the anomalies dependent on the site of the adhesions [4].

5.6. Postnatal assessment

The assessment includes a complete physical examination with attention to the cord, fingers and toes, face and skull, with recording of all defects and a search for fibrous strands [2]. All four limbs should be examined, even when the defect appears limited to one, checking for hypoplastic nails; recording is done with photographs, a diagram and a description [34]. The targeted examination includes the scalp (Adams-Oliver syndrome), the tongue and mandible (oromandibular-limb hypogenesis), cranial nerves VI and VII (Möbius sequence), the pectoral muscle and the chest when the defect is of the upper limb (Poland sequence), the heart, anus and genitalia when there is a major lower limb defect, and the hands and feet of the parents [34]. The history should cover three generations (limb defects, heart disease, deafness, eye abnormalities), maternal diabetes, exposure between 5 and 11 weeks (bleeding, misoprostol, retinoids, cocaine, valproate), twinning and invasive procedures [34]. The fresh placenta and membranes should be sent for examination [2, 10].

The Oxford Desk Reference recommends, in limb reduction defects in general, radiography of both upper or lower limbs and echocardiography and electrocardiography in infants and children, because 15% of children with limb reduction defects have congenital heart disease; it also notes that these investigations may not be necessary when there is confidence in the diagnosis of bands [34]. A full blood count with blood film is indicated in terminal transverse defects without a secure diagnosis, to exclude the macrocytic anaemia of congenital dyserythropoietic anaemia type I [13].

5.7. Genetic tests: indication and limits

In isolated ABS with physical evidence of bands, there is no indication for genetic testing directed at ABS itself, because there is no causal gene [2]. Genomic analysis (microarray, panel or exome/genome) is indicated when there are features suggesting a chromosomal or syndromic diagnosis: symmetric defects, internal anomalies, developmental delay, scalp defect or family history [34]. When Adams-Oliver syndrome is suspected, the panel should include ARHGAP31, DLL4, DOCK6, EOGT, NOTCH1 and RBPJ; the diagnostic yield is limited (30% in the European cohort of 194 probands, 36% in familial cases), so a negative result does not exclude the clinical diagnosis [6]. Sequencing does not detect exon deletions or duplications, whose proportion in Adams-Oliver syndrome is unknown, and variants of uncertain significance neither confirm nor exclude the diagnosis [13]. In familial ABS or a history suggestive of vascular fragility, study of COL3A1 in the parent with clinical suspicion is relevant [7]. In LBWC, chromosome and copy number variant (CNV) studies are usually normal: in 20 fetuses of a Chinese series with CNV-seq, microarray or karyotype, 18 were normal and 2 without a clear causal relationship; in a series of 96 wall defects, 8 of 60 conclusive tests showed a chromosomal anomaly (6 trisomies 18), but not all cases met LBWC criteria and it is unclear whether these were confined placental mosaicism [4, 25]. In EUROCAT, only 21% of ABS and 30% of LBWC had a recorded cytogenetic test [8].

5.8. Diagnostic algorithm

5.9. Prenatal and preimplantation diagnosis

Because ABS has no known genetic cause, there is no molecular prenatal diagnosis or applicable preimplantation genetic testing [2]. Prenatal diagnosis is by ultrasound, with a median gestational age at diagnosis of 21 weeks (15–26) in the cases operated on by fetoscopy [26]. In genetic phenocopies with an identified variant (Adams-Oliver syndrome, vascular Ehlers-Danlos syndrome), prenatal and preimplantation diagnosis follow the rules of the respective gene [7, 13].

6. Differential Diagnosis

6.1. Comparative table

6.2. Adams-Oliver syndrome

Adams-Oliver syndrome (AOS) is the most important genetic phenocopy, because the combination of terminal transverse defects with aplasia cutis is diagnostic of AOS, except when ABS reproduces it completely, especially if the bands were not seen on ultrasound or at delivery [13]. Constriction rings have been described in AOS and do not distinguish the two entities [13]. More useful are the location of the scalp defect (the vertex is typical of AOS and it is unusual for bands to cause focal scalp defects), the predominance of toes over fingers, congenital heart disease, cutis marmorata telangiectatica congenita and the presence of mild signs in the parents, such as hairless scarred areas or short distal phalanges [5, 13]. AOS is genetically heterogeneous: in the European cohort of 194 probands and families, NOTCH1 accounted for 10% of cases, DLL4 6%, DOCK6 6%, ARHGAP31 3%, EOGT 3% and RBPJ 2% [6]. The Oxford Desk Reference states that ARHGAP31 is the most frequent gene in non-consanguineous populations, which diverges from this cohort and from the GeneReviews chapter, in which NOTCH1 and DLL4 predominate; the 2018 cohort prevails [6, 13, 34]. In the review by Hassed and colleagues (385 published individuals and 13 new ones), central nervous system anomalies and congenital heart disease each occurred in 23%, CMTC in 19% and other vascular anomalies in 14%; haemorrhage was the cause of 5 of the 25 recorded deaths [24]. The DOCK6 form is associated with structural brain and ocular anomalies and intellectual disability [9, 13]. The recessive EOGT form (AOS4, 3p14.1) was identified by Shaheen and colleagues (2013) in 5 children from 3 consanguineous Arab families, with aplasia cutis of the scalp and terminal transverse defects of the toes (hypoplastic or absent nails, variably absent distal phalanges), septal heart disease in 2 of the 3 probands and absence of microphthalmia; the variants were homozygous (NM_001278689.2:c.620G>C p.(Trp207Ser), a 1-bp deletion and NM_001278689.2:c.1130G>A p.(Arg377Gln)) and the parents tested were heterozygous carriers [19]. Schröder and colleagues (2019) described a Turkish father and son from a family with multiple consanguinity, both homozygous for NM_001278689.2:c.404G>A p.(Cys135Tyr), and a German man homozygous for a splicing variant: the son had a parieto-occipital defect of the scalp and bone with brain herniation, small nails and tapering toes, the father only an extensive area of alopecia without limb defects, and neither had intellectual disability or ocular anomalies [19]. Father-to-son transmission of a recessive form in consanguineous families (pseudodominance) is one of the reasons why the apparent inheritance pattern is not sufficient to choose the genes to test [19]. The distinction has direct consequences: dominantly inherited AOS carries a 50% risk for the offspring of a carrier, and the recessive form 25% for siblings [13].

6.3. Limb–body wall complex

LBWC is distinguished from ABS by frequent internal anomalies, by limb defects that bands do not explain, by the short cord, by the continuity between the amnion and the skin of the defect and by persistence of the extraembryonic coelom [11, 23]. Overlap exists: EUROCAT recorded bands in some LBWC cases, classifying them as LBWC, and there are reports of LBWC and ABS in siblings [8, 53]. Twinning is a common factor, with an excess of monozygotic twins in LBWC [8]. On ultrasound, body stalk anomaly tends to show marked scoliosis, a short cord and adherence of the abdominal wall to the placenta [2]. The limb–body wall complex enters the differential diagnosis.

6.4. Other limb defects of genetic cause

Longitudinal defects, such as radial aplasia, belong neither to the band spectrum nor to AOS and point towards Holt-Oram, VACTERL, Okihiro (SALL4), Miller syndrome (DHODH), ulnar-mammary syndrome (TBX3), Fanconi anaemia or Roberts syndrome (ESCO2) [13, 34]. Split hand or foot (1 in 8000 to 25,000 newborns; about 15% of all reduction defects) usually has autosomal dominant inheritance with incomplete penetrance [34]. Cornelia de Lange syndrome (NIPBL and other cohesin genes) combines severe upper limb reduction defects with a characteristic face, growth retardation and intellectual disability [34]. Examination of the parents and the symmetry of the defects are the most useful clinical elements [34].

6.5. Isolated scalp and wall defects

Isolated aplasia cutis congenita occurs in about 1 in 3000 live births and has non-genetic causes (birth trauma, amniotic bands, vascular disruption, teratogens such as misoprostol, cocaine, methotrexate, angiotensin-converting enzyme inhibitors, thiamazole, benzodiazepines and valproate) and genetic causes (BMS1, Finlay-Marks syndrome due to KCTD1, focal dermal hypoplasia due to PORCN, dystrophic epidermolysis bullosa due to COL7A1, trisomy 13, Wolf-Hirschhorn syndrome, Johanson-Blizzard syndrome due to UBR1) [13, 54]. Apparently isolated aplasia cutis may belong to the Adams-Oliver spectrum, and the Oxford Desk Reference suggests detailed ultrasound scans of the digits and heart in the next pregnancy [54]. In the abdominal wall, isolated gastroschisis has a recurrence risk of about 1% and omphalocele is associated with aneuploidy in 30% of cases, whereas the wall defects of ABS are oblique and asymmetric and are accompanied by limb lesions [2, 12].

7. Treatments and Risk Management Strategies

7.1. General principles and evidence base

There are no guidelines from scientific societies for the management of ABS, and surveillance and decisions are individualised [2]. The evidence on fetal intervention comes from case reports and series gathered in systematic reviews, without randomised trials, and the evidence on postnatal surgery comes from single-centre retrospective series [26, 27]. There is no pharmacological therapy directed at ABS, and therefore there are no doses, FDA (Food and Drug Administration) or EMA (European Medicines Agency) labels or medicines authorised for this indication [2]. Management is organised in three phases: prenatal (diagnosis, staging, counselling and, in selected cases, fetoscopic release), perinatal (place and mode of delivery, resuscitation) and postnatal (surgery of the rings, hands, feet and craniofacial lesions, orthopaedics, rehabilitation and prostheses) [2, 55].

7.2. Counselling and prenatal surveillance

Counselling should explain the anomalies identified and the possibility of other anomalies not detected by ultrasound, and maintain prenatal care with increased fetal surveillance, including serial ultrasound scans of growth and of the affected areas [2]. Ferrer-Marquez and colleagues recommend that each examination include Doppler proximal and distal to the constriction and of the contralateral limb, and measurement of the circumferences of both limbs to quantify oedema [26]. In severe and life-limiting anomalies, counselling should include, clearly and without value judgement, the option of termination of pregnancy and neonatal palliative care, with social work support [2]. In EUROCAT, 33.7% of pregnancies with ABS and 85.8% of those with LBWC ended in TOPFA [8]. Delivery should take place in a hospital with radiology, neonatology and paediatric surgery when immediate intervention may be needed [2]. The team includes obstetrics, maternal–fetal medicine, neonatology, paediatric radiology, paediatric surgery and social work [2].

7.3. Fetoscopic release of bands: indications

Fetoscopic lysis, with laser or scissors, can halt the progression of the constriction and restore flow to the distal structures, saving a limb at risk or preventing fetal death when the cord is compromised [2]. The classic criteria for operating are based on the behaviour of arterial and venous flow and on the progression of oedema of the affected segment [26, 49]. The ideal candidate has an isolated constriction of one limb with abnormal but present distal Doppler flow (Hüsler stages 2b to 3a), without other structural anomalies [49, 56]. Gueneuc and colleagues do not recommend intervention when the fetus is extensively affected by bands and consider it for a fraction of cases with isolated limb constrictions [57]. Cord involvement is the strongest indication: Derderian and colleagues found the cord involved in 4 of 5 fetuses operated on, and the only one in which the cord band was not released died at 24 weeks [50]. Some centres restrict intervention to life-threatening situations, such as cord involvement; the Mannheim centre adopted this policy after observing fetal death within days to weeks in untreated cases of cord constriction [48]. Because cord involvement is difficult to see before surgery, the systematic review recommends always inspecting the cord during fetoscopy [26].

7.4. Technique

In the review of 37 cases operated on between 1997 and 2022, one access port was used in 75.6% of cases and two in 24.3%; in one case, the technique was hybrid, with laparotomy and exteriorisation of the uterus [26]. The fetoscopes were 1.0 to 3.8 mm in diameter (median 2.4 mm), with ≤2 mm in 29.7% [26]. Division was performed with laser in 41.6% (mainly YAG — yttrium aluminium garnet — and, in 3 cases, diode laser), with scissors only in 30.5% and with a combination of laser and scissors or forceps in 27.7% [26]. Anaesthesia was general in 48.5%, regional with maternal sedation in 39.3% and local in 12.1% [26]. When the amniotic fluid is heavily blood-stained, partial amniotic carbon dioxide insufflation (PACI) allows visualisation; the Mannheim centre reports more than 300 interventions with this technique without gas embolism [48]. The median gestational age at surgery was 22 weeks (18–29), and the median interval between diagnosis and procedure 7 days (1–63) [26]. In the Strasbourg series, for example, three fetuses were operated on at 23 weeks and 5 days, 26 weeks and 5 days and 18 weeks and 3 days, two with a laser fibre through a single trocar and one with scissors [58].

7.5. Results of fetoscopic release

The results of these series are not comparable with one another, because they overlap (the reviews include the cases of the individual series), use different selection criteria and have no control group [26]. The authors themselves consider it likely that the success rate is overestimated by publication bias, because unsuccessful cases tend not to be published [26, 57]. The PROM rate was higher than in other fetal surgeries (51.3% against 25–30%), and was 27.2% with fetoscopes of ≤2 mm against 61.5% with larger fetoscopes; the authors acknowledge that the membranes of these patients may have intrinsic properties favouring rupture [26]. Comparison with untreated natural history rests on assumptions, because there are no prospective series of fetuses with unoperated constriction [26].

7.6. Fetal postoperative care

After fetoscopy, the pregnancy requires obstetric surveillance directed at PROM, preterm labour, chorioamnionitis, haemorrhage and placental abruption [26, 48]. In the Mannheim case, the mother received prophylactic tocolysis with atosiban for 24 hours and intravenous clindamycin for 3 days, according to the centre's protocol; this is a local practice, without a published general recommendation [48].

7.7. Neonatal period

The newborn with oligohydramnios sequence and pulmonary hypoplasia should receive full ventilatory support, because lung morphogenesis continues [10]. Vascular compromise of a limb diagnosed after birth may require urgent surgery [2]. In Weinzweig's experience, progressive compromise due to lymphatic–venous and/or arterial obstruction with soft-tissue necrosis was treated with immediate decompression to drain the lymphoedema, staged excision of the band, closure with Z-plasty and topical antimicrobials on the open wound [46].

7.8. Surgery of constriction rings

Superficial rings do not need treatment, and deep ones are treated by excision and reconstruction [60]. Smith describes the typical indication: a deep, partially constricting residual groove encircling a limb and limiting distal vascular or lymphatic return, treated by Z-plasty of the skin [10]. The traditional approach was excision in two or three stages, so as not to compromise the distal circulation [60, 61]. Subsequent series showed the safety of single-stage correction:

The review by Wire and colleagues (2026) describes a range of techniques from simple excision of the rings to on-top-plasties in digital deficiencies, with an individual approach that weighs the urgency of release, neurovascular preservation, viability of the distal part and function [55].

7.9. Peripheral nerves

In complete palsies due to compression of a nerve under the ring, Jones and colleagues released the bands at 3 and 6 months without neurological recovery over 7 years; they recommend release as early as possible and, if exploration shows significant compression, excision of the damaged segment with primary nerve repair or grafting [45].

7.10. Clubfoot

Clubfoot associated with ABS is treated first-line with the Ponseti method [63]. In a Kentucky series of 21 feet in 12 patients, initial correction was achieved in 95.2%, with percutaneous Achilles tenotomy in 81% and recurrence in 33.3%, and all but one patient had plantigrade, flexible feet after 3.9 years [63]. In a 20-year Dallas series, comparing 43 feet with ABS with 320 idiopathic ones, recurrence was 62.8% against 37.2% (p = 0.001) and the result was "good" in 41.9% against 69.4%, "fair" in 34.9% against 26.9% and "poor" (complete posteromedial release) in 23.3% against 3.8% (p < 0.001) [28]. These data justify informing parents that clubfoot associated with bands has more recurrences and a greater need for surgery [28].

7.11. Hand, craniofacial defects and rehabilitation

Digital amputations and pseudosyndactyly require hand surgery, ranging from excision of the rings to on-top-plasties in digital deficiencies, according to each child's anatomy [55]. Craniofacial, eyelid and wall defects require neurosurgery, plastic surgery and ophthalmology [2]. Limb amputations are referred to physical and rehabilitation medicine and prosthetics; the studies registered on ClinicalTrials.gov that include children with limb differences due to bands evaluate 3D-printed prostheses and adaptive games, not interventions on ABS [64].

7.12. Regulatory table

7.13. Developments in the last 12 months

There have been no regulatory procedures, because there are no drugs in development for ABS. Among the trials registered on ClinicalTrials.gov (searched on 29 October 2026), there are no studies directed at ABS, at fetoscopy for bands or at LBWC; the records with the term "amniotic band" refer to 3D-printed prostheses (NCT04110730, recruiting, 40 participants), to a withdrawn study of neural and motor performance (NCT04241588) and to adaptive games for upper limb differences (NCT05981664, recruiting, 20 participants) [64]. In the literature published between April 2025 and October 2026 (observational studies and reviews, without trials), the following stand out: the proposal of prenatal criteria for LBWC based on population data from Alberta [4], two Chinese series on the first-trimester ultrasound diagnosis of LBWC [25, 52], a surgical review of constriction band syndrome [55], a Brazilian survey of women with an affected pregnancy [65] and a letter on ABS mimicking genetic limb reduction defects [66].

7.14. Pregnancy, perioperative care and transition

The affected pregnancy itself is the context of risk, with PROM, preterm birth and low birth weight [2]. In twin pregnancies treated by fetoscopic laser, early gestational age and chorioamniotic separation increase the risk of post-procedure bands, which should be included in counselling before the laser and in surveillance after it [41]. Transition to adulthood centres on limb function, prostheses and the sequelae of multiple surgeries; the sources consulted do not describe specific transition programmes.

8. Reproductive Options and Family Counselling

8.1. Recurrence risk in isolated ABS

ABS is, as a rule, a sporadic event in a normal family, and the recurrence risk is usually described as negligible [10]. The Oxford Desk Reference gives a very small recurrence risk, below 2% [34]. Isolated transverse defects of a single limb are very probably sporadic, with a low risk for siblings and for the offspring of the affected child [34]. The body wall complex is also probably sporadic, with a low recurrence risk [12]. These figures apply after a secure diagnosis; the main source of error in counselling is attribution of a genetic phenocopy to bands [13].

8.2. Situations that alter the risk

Familial occurrences of ABS are rare and, in part, poorly documented or with a revised diagnosis [35]. OMIM gathers some: father and son with a ring on the terminal phalanx of the same digit in two families (Gellis, 1977), congenital toe amputations in an infant and the mother (Etches, 1982), two families with amputations, rings and anencephaly in several relatives (Lubinsky, 1983) and three families with two cases each of terminal transverse defects of the arm, suggestive of constriction (Pauli, 1985), whose authors concluded that Mendelian inheritance was not tenable, but that a genetic contribution was more likely than chance [14]. Siblings with LBWC and ABS without an identified maternal factor have been described [53], as well as familial ABS in children of mothers with connective tissue disorders and two paternal half-siblings with ABS who inherited a COL3A1 variant from their father [7]. In this last scenario, the risk for each child of a carrier of vascular Ehlers-Danlos syndrome is 50% of inheriting the variant, with an unquantified specific risk of ABS [7]. If the diagnosis is revised to Adams-Oliver syndrome, the risk follows the gene: 50% for the offspring of a carrier of a variant in a dominant gene, with incomplete penetrance and variable expressivity, and 25% for siblings in the recessive forms due to DOCK6 or EOGT [13]. Therefore, even with a negative family history, examination of the scalp and limbs of the parents is recommended, possibly with radiographs of the hands and feet [13].

8.3. Next pregnancy

In isolated ABS there is no specific prenatal or preimplantation test, because there is no genetic alteration to test [2]. In a subsequent pregnancy, the routine anomaly scan is the means of surveillance; when the previous diagnosis was isolated aplasia cutis or there was doubt with the Adams-Oliver spectrum, the Oxford Desk Reference suggests detailed ultrasound scans of the digits and heart [54]. The calvarial defects of Adams-Oliver syndrome can raise maternal serum alpha-fetoprotein and amniotic fluid acetylcholinesterase [13]. In families with an identified pathogenic variant (COL3A1 or Adams-Oliver syndrome genes), prenatal diagnosis and preimplantation genetic testing are possible [7, 13]. Intrauterine procedures and early fetoscopic laser increase the risk of post-procedure bands, which forms part of the informed consent for those procedures [26, 41].

8.4. Genetics clinic

Pape and Gorla consider that, ABS being sporadic and non-hereditary, a medical genetics consultation is of limited use [2]. This position applies to the typical case with documented bands; assessment by medical genetics remains indicated when visible bands are lacking, the defects are symmetric, there is a vertex scalp defect, internal anomalies, developmental delay or a family history, because in these situations the distinction from Adams-Oliver syndrome, other limb defects of genetic cause and vascular Ehlers-Danlos syndrome changes the recurrence risk [7, 13, 34].

9. Special Considerations: Population Diversity and Epidemiology

9.1. Europe

The 2023 EUROCAT study, with 30 population-based registries from 15 countries between 1980 and 2019 (including the Portuguese National Register of Congenital Anomalies, RENAC), estimated a birth prevalence, including live births, stillbirths and TOPFA, of 0.53/10,000 births for ABS (95% CI 0.50–0.57; 866 cases) and 0.34/10,000 for LBWC (0.31–0.37; 451 cases) [8]. Orphanet adopts these values for Europe (5.3 and 3.4 per 100,000) [1, 3].

Source: Bergman et al. 2023, table 1 [8]. Prevalence was higher in the United Kingdom registries (LBWC 0.64 against 0.20/10,000 in the others), lower in Tuscany (ABS 0.08) and Valencia (0.10) and higher on Réunion Island (1.46), in Vaud (1.28), in Auvergne (1.23) and in Wales (1.22); for LBWC, the highest values were those of the North of England (1.04) and Wessex (0.93) [8]. The authors attribute these differences mainly to differences in ascertainment and coding, and consider that the figures underestimate the real prevalence, owing to the lack of consensus criteria, of a specific code for LBWC and of complete notification of anomalies [8]. The article does not present separate values for Portugal. Other European estimates are that of Finland (1.12/10,000 births) and the Spanish ECEMC estimate, used in the epidemiological separation between ABS and the body wall complex [8, 31].

9.2. North America

In Atlanta (1968–1982), the prevalence was 1.16/10,000 live births, with 0.91 in males and 1.44 in females and 1.76 times higher in Black children, and the authors estimated that the real prevalence would approach 3/10,000 live births, taking underdiagnosis into account [22]. In Alberta, the combined prevalence of ABS, LBWC and wall defects was 1.08/10,000 births (1980–2012), and that of LBWC by the Van Allen criteria 0.47/10,000 (1997–2019) [4, 35]. The EUROCAT review cites 0.19/10,000 live births in Canada and 2.03/10,000 in Western Australia [8]. The classic estimates of 1 in 1200 to 1 in 15,000 live births are of order-of-magnitude value, because they mix different definitions and populations [33, 43]. A 2026 surgical review places constriction band syndrome between 0.5 and 1.1 per 10,000 births [55].

9.3. South America and Brazil

ECLAMC (Latin American Collaborative Study of Congenital Malformations) recorded a prevalence of 0.89/10,000 births in South America (1967–1997; 284 non-syndromic cases), with constriction rings in 66.9% and reduction defects in 84.5% [8]. In the study by Orioli and colleagues (2003), the prevalence of the ADAM sequence among live births and stillbirths was about 1 in 11,200 births between 1982 and 1998; half the cases had only reductions or rings of the digits, there was an excess of cases in the high-altitude Andean population and among stillbirths and neonatal deaths, and the sequence was more frequent in first-borns and in children of mothers with febrile illness, medication or vaginal bleeding in the 1st trimester [14]. In Brazil, an online survey of 22 women with a pregnancy affected by ABS (voluntary sample, without prevalence value) showed prenatal ultrasound diagnosis in 54.5% of cases, perception of well-informed professionals and full support in only 40.9%, fetal surgery in one case, a predominance of caesarean sections and more frequent involvement of the hands and arms [65].

9.4. Other regions

Orphanet records, for LBWC, birth prevalences of 3.0/100,000 in Australia and 2.5/100,000 in Japan [3]. A Mexican series of 50 prenatal cases showed a mean maternal age of 25.7 years and 54% primiparas [42].

9.5. Special populations

Twinning is the most consistent risk factor: 5.9% of ABS and about 10% of LBWC in EUROCAT belonged to multiple pregnancies, against 0.91–1.44% in the European population, and all pairs with ABS were discordant [8]. Pregnancies undergoing fetoscopic laser for twin–twin transfusion syndrome have a specific risk of post-procedure bands (2.2% in Leiden) [41]. Mean maternal age was 27.4 years in ABS and 28.5 in LBWC, and 55% of ABS cases were the mother's first child [8].

9.6. Resources

ERN ITHACA (European Reference Network on Rare Malformation Syndromes, Intellectual and Other Neurodevelopmental Disorders) is the relevant European network for rare malformation syndromes [29]. The EUROCAT network, coordinated by the Joint Research Centre of the European Commission, maintains population surveillance of congenital anomalies, with Portuguese participation through RENAC [8]. Among patient associations, Reach supports, in the United Kingdom, children with upper limb differences and their families [67].

10. Illustrative Clinical Case

Riehle and colleagues (Mannheim, Germany) described a 31-year-old woman, with one previous pregnancy and one delivery, referred at 22 weeks and 1 day after a routine ultrasound had shown amniotic bands; she had had vaginal bleeding in the 1st trimester [48]. The ultrasound revealed a retroplacental haematoma, partial placental abruption and almost complete chorioamniotic separation, with the amnion floating freely and a normal fluid volume [48]. Multiple bands, originating from the detached amnion, adhered to the fetus and the cord; several loops of the cord were trapped in amniotic and placental tissue, with increased umbilical venous velocities, which led to suspicion of cord constriction; the right leg was strangulated, with oedema down to the foot and reduced distal venous flow; and the left foot passed through the detached placental segment [48]. At 22 weeks and 2 days, under maternal–fetal general anaesthesia, the team performed fully percutaneous fetoscopic surgery with three 11 Fr sheaths, a 30° fetoscope, and 3 mm forceps and scissors; as the fluid was heavily blood-stained, they resorted to partial amniotic carbon dioxide insufflation (pressure of 8 mmHg) to obtain visualisation [48]. All the bands of the leg and cord and the detached placental segment were divided, and the distal segment of the leg immediately regained its colour [48]. Figure 4 of the article shows the annular bands encircling the cord and placenta, the foot trapped in the placenta, the tight band on the leg and the reperfusion after division (https://pmc.ncbi.nlm.nih.gov/articles/PMC11763431/figure/children-12-00020-f004/) [48]. The pregnancy was prolonged by 23 days, until a caesarean section at 25 weeks and 4 days because of contractions; the newborn had no band remnants, only a circumferential impression on the right leg, and presented transient peroneal nerve palsy with foot drop, which resolved in the first year with physiotherapy (Figure 5: https://pmc.ncbi.nlm.nih.gov/articles/PMC11763431/figure/children-12-00020-f005/) [48]. The infant was discharged from the neonatal intensive care unit at 11 weeks and, at almost 3 years, had normal development and gait, without sensory or motor deficits [48]. The authors interpret the origin as traumatic and exogenous, given the early bleeding and the formation of the bands from the detached amniotic sac [48]. This case combines the two most frequently cited indications for intervention, cord involvement and a limb with compromised distal flow, and was performed in a centre with experience of more than 300 procedures with the same technique; the general anaesthesia, the carbon dioxide insufflation and the tocolysis and antibiotic regimen are choices of that centre and not a standardised approach, and the favourable outcome does not eliminate the risks of PROM, preterm birth and fetal death described in the series [26, 48].

11. Prognosis and Long-term Follow-up

11.1. Prognosis

The prognosis depends on the extent of the lesions and ranges from minor cosmetic defects to lethal anomalies [2]. Isolated constriction has a good prognosis and normal life expectancy, and the anomalies visible on the surface are usually the only ones [2, 10]. Cord involvement is the main risk factor for stillbirth [2, 47]. In EUROCAT, 52.7% of ABS cases were live born, 13.6% were stillbirths and 33.7% ended in TOPFA; among live births, survival to the first week was 94% [8]. In LBWC, 85.8% ended in TOPFA, 8.2% were live born and 6.0% were stillbirths, and survival to the first week of live births was 5%; Smith states that the great majority miscarry spontaneously and the rest are stillborn [8, 11]. In pulmonary hypoplasia due to oligohydramnios, ventilatory support can lead to an excellent prognosis [10]. Long-term functional results depend on the amputations, on the response of the clubfoot (more recurrences than in idiopathic clubfoot) and on nerve lesions, which may not recover even with early release [28, 45].

11.2. Surveillance table

There are no standardised surveillance intervals for ABS; the examinations below bring together the recommendations of the sources, with individual intervals where no published value exists.

11.3. Long-term follow-up

Follow-up is directed at the sequelae: hand and foot surgery, growth of the operated segments, prostheses, nerve function and scars, with continuous rehabilitation [27, 55]. The sources consulted do not describe cohorts of adults with ABS or long-term quality-of-life data.

12. Summary and Final Considerations

Amniotic band sequence is a sporadic disruption, without a causal gene, in which fibrous strands of amniotic origin constrict, amputate or tether parts of the fetus or the cord, with a European birth prevalence of 0.53 per 10,000 and a predominance of asymmetric limb lesions, to which atypical facial clefts, neural tube defects and wall defects may be added. Its aetiology remains debated between amnion rupture, vascular disruption and early embryonic defect, and twinning, intrauterine procedures and chorioamniotic separation are the most consistent risk contexts. The limb–body wall complex, with internal anomalies, short cord, severe scoliosis and lethal course, is a borderline entity with its own criteria under revision. Diagnosis rests on the physical demonstration of bands and the exclusion of phenocopies: Adams-Oliver syndrome, with aplasia cutis of the vertex, heart disease and dominant or recessive transmission, is the most important, and vascular Ehlers-Danlos syndrome has been described as a familial predisposition. In the prenatal period, staging by ultrasound and Doppler identifies fetuses with limb constriction and compromised but present distal flow, or with cord involvement, who may benefit from fetoscopic release; the published series show preservation of function in about three quarters of survivors, at the cost of PROM in half the cases and frequent preterm birth, without randomised trials and with probable publication bias. After birth, single-stage release of the rings is safe in the published series, clubfoot responds to the Ponseti method with more recurrences than idiopathic clubfoot, and complete nerve palsies require early release. The recurrence risk is below 2% when the diagnosis is secure, and counselling depends above all on excluding the genetic causes that mimic the sequence.

13. References

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