The association of umbilical cord complications and variable decelerations with acid-base findings.

Variable decelerations during the last 2 hours of labor were associated with an abnormally positioned umbilical cord at delivery in 52% of cases. In cases where an abnormally positioned umbilical cord was seen at delivery, 89% had been preceded by variable decelerations. Cord compression resulted in an A-V difference in pH that was significantly increased when compared to a control group. This was mainly due to a decrease in the pH of the umbilical artery. The pathophysiology of cord compression is discussed.