Combined decelerations--clinical significance and relation to uterine activity

A combined fetal heart rate deceleration consists of a first (either early or variable) component and a second (late) component. All patients with combined decelerations during a 2-year period of routine fetal monitoring were studied. The incidence was 1.1% (70 patients). Most patient were at low risk, and the combined decelerations appeared predominantly late in the first stage of labor. In all but 5, labor was stimulated by oxytocin infusion. In two thirds of patients, intrauterine pressure was recorded; uterine hyperactivity was found in 78.7%. Combined decelerations with a total loss of at least 90 beats and lasting for at least 60 seconds were associated with low fetal scalp pH. Ten percent of infants were born in the occiput posterior position. The results indicate a relation between abnormal uterine activity and combined fetal heart decelerations. This type of deceleration could serve as a warning signal of excessive oxytocin administration.