Compression-related defects from early amnion rupture: evidence for mechanical teratogenesis.

The features of 27 cases of limb/body wall deficiency (formerly termed cyllosomus and pleurosomus) were evaluated and the anomalies were interpreted as being band-related defects and/or compression-related defects. The latter included limb deficiency, body wall deficiency, neural tube defects, scoliosis, postural deformations, growth deficiency, and short umbilical cord. It is hypothesized that the single event of early amnion rupture can explain both the band-related defects and the compression-related defects. Experimental animal studies are in accord with this hypothesis; amnion puncture of rat fetuses during early gestation produces a comparable array of defects. The term amnion rupture sequence is suggested to describe the overall pattern of malformation that results from amnion rupture whether these defects are band related, compression related, or a combination of the two. There is considerable variation in the phenotype of amnion rupture sequence, with limb/body wall deficiency representing the more severe end of the spectrum. It is important to recognize and correctly diagnose amnion rupture sequence because it is usually a sporadic event.