Accuracy of strategies for monitoring fetal heart rate in labor.

We investigated whether the accuracy of auscultation could be improved with the use of a heart rate meter. Six fetal heart rate (FHR) traces were presented in a random sequence to 30 subjects using a customized computer program in each of three modalities: auscultation by counting alone, auscultation with the aid of an FHR meter, and visual assessment. The following characteristics were assessed: baseline rate, baseline variability, periodic change, and interpretation of the trace. For baseline rate, counting was associated with consistent underestimation of the FHR, which became more evident as the heart rate increased. The variation observed with each method was greatest with counting. For baseline variability, the proportion of correct responses using a meter was comparable to visual assessment, whereas counting was significantly less effective in 4 of 6 traces. For periodic change, the use of a meter was superior to counting in 4 of 6 traces, but both were inferior to visual assessment in 4 of 6 traces. In the interpretation of the trace, the use of a meter was again superior to counting, but both were inferior to visual assessment. Discrepancies were most marked in the least reassuring traces. Assessment of the FHR is significantly more accurate with the aid of a heart rate meter, and reduces interobserver variation.