Prenatal diagnosis of the two-vessel cord: implications for patient counselling and obstetric management.

The study was designed to investigate the implications of the sonographic diagnosis of the two-vessel umbilical cord for patient counselling and pregnancy management. Retrospective analysis was carried out of prenatal findings and pregnancy outcomes when a two-vessel cord was diagnosed in utero. Eighty-two fetuses each with a single umbilical artery were diagnosed by ultrasound. Ten were aneuploid, including nine with visible structural defects and one with early onset intrauterine growth retardation. Of the remaining 72, 31 had other anomalies diagnosed postnatally; 27 of these had structural defects detected on ultrasound examination. However, in nine of these 27 sonographically abnormal fetuses, one or more major structural defects were missed by ultrasound examination. Among the 45 chromosomally normal fetuses with no visible defects on scan, four had anomalies diagnosed after birth. Among the chromosomally normal singletons, six of 22 with other anomalies seen on scan and seven of 38 with no other visible defects on scan had intrauterine growth retardation. Among chromosomally normal twins, one of two with other anomalies seen and two of five appearing otherwise normal had intrauterine growth retardation; one twin set was delivered at 23 weeks after the demise of both twins. Karyotyping is recommended whenever a two-vessel cord is seen in association with symmetric intrauterine growth retardation or any other defect. The fetus diagnosed with a two-vessel cord and any other anomaly by ultrasound often has additional structural defects not seen on scan. The fetus with an isolated two-vessel cord on scan seldom has unrecognized major anomalies, but is at risk for intrauterine growth retardation.