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 pres ented in a random sequence to 30 subjects using a customized computer progr am in each of three modalities: auscultation by counting alone, auscultatio n with the aid of an FHR meter, and visual assessment. The following charac teristics were assessed: baseline rate, baseline variability, periodic chan ge, and interpretation of the trace. For baseline rate, counting was associ ated with consistent underestimation of the FHR, which became more evident as the heart rate increased. The variation observed with each method was gr eatest with counting. For baseline variability, the proportion of correct r esponses using a meter was comparable to visual assessment, whereas countin g was significantly less effective in 4 of 6 traces. For periodic change, t he 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 th e trace, the use of a meter was again superior to counting, but both were i nferior to visual assessment. Discrepancies were most marked in the least r eassuring traces. Assessment of the FHR is significantly more accurate with the aid of a heart rate meter, and reduces interobserver variation.