Abnormalities of the umbilical cord, related to morphology, placental insertion, number of vessels and primary tumors, can influence the perinatal outcome and may be associated with other fetal anomalies and aneuploidies. The chapter investigates the most important congenital anomalies of this structure. Single umbilical artery appears to be associated with ventricular septal defects and conotruncal anomalies, hydronephrosis, dysplastic kidneys, esophageal atresia, spina bifida, holoprosencephaly, diaphragmatic hernia, and cystic hygromas. Velamentous insertion of the cord can be associated with trisomy 21, spina bifida, ventricular septal defects, and esophageal atresia. A hypoplastic umbilical artery has an artery-to-artery diameter difference of more than 50%; described anomalies include trisomy 21, polyhydramnios, congenital heart disease, and fetal growth restriction. Pseudocysts are more common than true cysts, and they are strongly associated with chromosomal defects and other congenital anomalies, especially omphalocele, hydrops, and trisomy 18. Other benign masses are teratomas, angiomyxomas, and patent urachus. Alterations in morphology and ultrastructure of the umbilical cord should extend the investigation, since there are associations with chromosomal anomalies.