Intrapartum fetal heart rate monitoring. V. Fetal heart rate patterns in the second stage of labor.

A total of 1,755 fetal heart rate (FHR) tracings of the second stage of labor was analyzed. The FHR patterns were classified according to the behavior of the baseline FHR and are listed in decreasing order of benignity: normocardia, transitory bradycardia, tachycardia, persistent bradycardia, and progressive bradycardia. Each category was further subdivided into four groups on the basis of association or nonassociation with early, variable, or late decelerations. Cord compression pattern were noted in over 50% of the FHR tracings and account for the majority of low Apgar scores and fetal acidosis. FHR abnormalities occurred in 91% of second-stage labor patterns, and were mild in most cases or of too short duration to influence fetal outcome. An effort was made to establish therapeutic guidelines based on the morphologic features, prognostic grading, and the etiology of the FHR patterns in the second stage of labor.