Giant cystic umbilical cord associated with patent urachus and intrauterine fetal demise.

True cystic structures within the umbilical cord are rare, and when they persist into the second and third trimester, they are often associated with an abnormal karyotype or other developmental abnormalities. Clinically significant pseudocysts resulting from massive edema of the umbilical cord have been associated with a congenitally patent urachus. We present a case of intrauterine fetal demise at 28 weeks' gestation in which cystic dilatation of the umbilical cord was diagnosed prenatally by ultrasound imaging. At autopsy, a congenitally patent urachus was contiguous with the massively edematous umbilical cord.