The association between umbilical cord anomalies and chromosomal abnormalities has received little attention in the literature. In this report, we present two cases of umbilical cord pseudocyst incidentally detected by ultrasound prior to genetic amniocentesis performed for the indication of advanced maternal age. In the first case it was only the initial abnormal finding in a 21-week fetus ultimately found to have a trisomy 18. In the second case, detected at 26 weeks, the karyotype was normal and a healthy normal neonate was delivered at term. The finding of a umbilical cord cystic mass during prenatal sonographic examination should alert the clinician to the increased risk of aneuploidy.