Abstract
BACKGROUND: Umbilical cord cysts are rare and the reported associations with abnormal foetal outcomes present challenges in antenatal diagnosis and management. KEY FINDINGS: We report a case of a large umbilical cord cyst detected in the second trimester, with no communication to the foetal bladder. Third trimester review demonstrated oedematous change in the umbilical cord and significantly reduced umbilical artery flow necessitating delivery by emergency caesarean section. Postnatally, the infant was found to have a patent urachus. DISCUSSION: This case underlines the importance of antenatal ultrasound surveillance in pregnancies complicated by umbilical cord cysts, limitations in definitive diagnosis and features of cord compression that have not been previously reported.