Amniotic bands are included in the amnion rupture sequence that comprises a series of malformations, the denomination of which depends on the etiologic hypothesis. The observed anomalies are thought to be due to a rupture of the amnion during the first trimester of gestation, resulting in adhesions between the amnion and the fetal skin, and in some cases, small strands of amnion encircling developing limbs, leading to annular constrictions, and bands between torn amnion and chorionic mesenchyme. Besides annular constrictions, pseudo-syndactyly, intra-uterine amputations, and umbilical cord constrictions may also be seen. In addition, the decrease in amniotic fluid and/or a possible tethering of a limb by an amniotic band may result in a decrease in fetal movements, and in scoliosis, foot deformity, lung hypoplasia, and hydrops. The amnion rupture sequence is rare, occurring in 1 to 4 newborns in 100,000. It is a sporadic disease, with rare exceptions: a few affected families have been described, with a likely autosomal dominant heredity. The clinical features of affected individuals from these rare families do not differ from those of the sporadic cases: no two affected foetuses will have exactly the same features, and there is no single feature that consistently occurs. Examination of the placenta and membranes leads to the diagnosis, which is made when aberrant bands are observed and possible remnants are noted at the placental base of the umbilical cord. The amnion rupture sequence must be differentiated from the Adams Oliver syndrome, an autosomal dominant anomaly characterized by transverse limb reduction defects, aplasia cutis congenita over the posterior parietal region with an underlying bone defect, and cutis marmorata. Although the pathogenesis of the amnion rupture sequence is still being debated, it is accepted by most authors that it has a pathogenetic mechanism different from that of the limb body wall complex (LBWC). The LBWC associates severe limb reduction defects, thoracic and/or abdominal coelosomia and unusual facial clefts with amnion adhesions, encephalocele or exencephaly.
Last update: July 2005
- Dr Elisabeth ROBERT-GNANSIA