A case of fetal vesicoallantoic cyst in the umbilical cord.

A vesicoallantoic cyst in the umbilical cord was detected by fetal ultrasonography at 16 weeks of gestation. The blood flow through the umbilical vessels was evaluated with periodic color Doppler ultrasonographic examinations because compression by the cyst may cause reduction in blood flow and lead to fetal death. After disappearance of the cyst, the infant was delivered vaginally. Retrograde cystography revealed a narrow channel between the bladder and the navel, confirming patent urachus, which was resected without any complications.