Vascular anomalies of the umbilical cord are amongst the most frequent congenital malformations, their incidence being 0.2% to 1.4%. As a result of the latter the risk of occurrence of other malformations and chromosomal anomalies is markedly elevated. Between January 1977 and July 1987 a total of 78 cases (0.51%) of umbilical cord vascular anomalies were recorded at the Department of Gynaecology of the University of Heidelberg. Malformations occurred in 37% of the foetuses involved. 28% showed retarded growth and 9% had an abnormal set of chromosomes. Anomalies of the urinary tract and malformations of the thoracic organs were very frequent. Total mortality after the 28th pregnancy was about 14%. Currently available high-resolution real-time ultrasound equipment can show up even prenatally pathological variations of the umbilical vascular pedicle (e.g. a single umbilical artery). Because of the manifold risk involved, routine ultrasound control is recommended. If this anomaly is diagnosed, the pregnancy should be classified and treated immediately as a high-risk pregnancy.