Thrombosis of the right umbilical artery, presumably related to the shortness of the umbilical cord: an unusual cause of fetal distress.

This case report concerns a late pregnancy complication, clinically apparent as severe variable decelerations in the first stage of labor. Emergency cesarean section delivered a mildly asphyxiated full-term newborn infant. Examination of the umbilical cord revealed a thrombus of the right umbilical artery, near the fetal side, confirmed by histological examination. The total length of the umbilical cord, only 30 cm, was below the limit necessary for uncomplicated delivery of the fetus near term. Transient stretching during fetal descent is thought to be responsible for constriction of the umbilical arteries, blood flow sludging and thrombosis. Although only a few cases have been reported, thrombosis of the umbilical vessels has to be considered whenever the fetal heart rate pattern shows unexplained variable decelerations.