Characteristics of fetal heart rate changes during the expulsive stage of bovine parturition in relation to fetal outcome

Abstract

Objective To characterize fetal heart rate (FHR) patterns of nonacidotic (N-AC) and acidotic (AC) calves during the expulsive stage of parturition. Animals 32 calves born to heifers, either unassisted or by moderate traction. Procedure Cardiotocograms (CTG) evaluated qualitatively (visual) and quantitatively by a moving window technique (width 10, shift 5 minutes) for baseline FHR, variability, and periodic alterations (accelerations and decelerations). Results Significant differences were apparent between increase in baseline FHR of N-AC and AC calves; change in FHR (Δ-FHR), taking into account individual FHR, is a more discriminating parameter. The predominant reaction to uterine contraction is a decrease in FHR; variable decelerations were the most common type in both groups, and late decelerations were seen only in AC calves. Additional characteristics of variable decelerations were more frequently seen in AC calves. Conclusions CTG parameters during expulsion can discriminate between AC and N-AC calves, but specific characteristics are not exclusively restricted to AC or N-AC calves. Clinical Relevance CTG recordings during bovine parturition in cattle provide information on the fetal condition and can be used in the future to study the effects of medication and manipulations to the fetus. (Am J Vet Res 1996;57:1373-1381)