Is fetal heart rate monitoring sufficiently sensitive to detect changes during labour?

Although fetal monitoring is a common clinical procedure, there is little quantitative evidence that it can detect changes occurring during labour. We present quantitative data comparing the first and second stage of labour, from 21 labours resulting in a normal fetal outcome. A range of fetal heart rate variables was calculated from the output of a fetal heart rate monitor. Significant changes were detected in baseline fetal heart rate (P less than 0.005), heart rate variability (P less than 0.05), number of dips (P less than 0.01) and their depth (P less than 0.01). The results encourage confidence in the sensitivity of fetal monitoring for the detection of changes in a number of fetal heart rate variables during the course of labour.