The Occurrence of Supernumerary Umbilical Cord Vessels: A Review for Practicing Clinicians.

: The umbilical cord normally contains two arteries and one vein. The presence of supernumerary-four or five-umbilical cord vessels is a rare phenomenon, with few cases reported in the literature. The majority of cases are detected postnatally. However, given their potential association with developmental abnormalities, primarily severe cardiac anomalies and genetic disorders, the prenatal diagnosis of supernumerary umbilical cord vessels may have clinical relevance. : A review of the clinical phenomenon of the four-vessel umbilical cord and its complications was conducted using case studies and literature reviews in PubMed from 1977 to the present and in Google Scholar from 1966 to the present. : Among the 24 reported cases, 7 cases were associated with malformations, 8 cases were detected antenatally, and 16 cases postpartum. Among the eight antenatally diagnosed cases, only one had a congenital malformation, hydrops fetalis. Among the postnatally diagnosed cases, six had congenital abnormalities: three were cardiovascular, two were associated with hydrops, urinary, gastrointestinal, and skeletal disorders, hypoplastic corpus callosum, and dysmorphic facial features. Four-vessel umbilical cords are more frequent than previously thought, as they can be easily overlooked during the mandatory ultrasound examination. A review of the literature revealed a correlation between supernumerary umbilical cord vessels and major congenital malformations, underscoring the significance of prenatal diagnosis; however, the four-vessel cord may not always be indicative of a serious condition.