[A fetal soft marker in obstetric ultrasonography: single umbilical artery]

The recent advancement in the field of ultrasonography allows for the prenatal precocious diagnosis of an ever increasing number of congenital defects found in various areas of the foetal body. These phenotype variants (markers) and/or morphological anomalies reveal in the majority of cases of a foetus with chromosome defects. They represent ''alarm bells'' that intrigue us to uncover any average case with more tests. It is for this that many more efforts are made to identify echographical markers which allow us to select among the pregnant women those that are not at risk and to advise those that may be of the existence of a specific cytogenetic test. One of these markers is actually represented by the single umbilical artery. This anomaly is made up of the presence of only two vessels (an artery and a vein) at the level of the umbilical cord, and its lack of an artery. The clinical meaning of this pathology is not yet completely known today. Often, in fact, when isolated, it is not associated with a chromosome defect and to other foetal pathologies. When, however, it is presented as associated to other soft markers or other structural anomalies, the risk of a chromosome defect is notably higher.