Advances in electronic fetal monitors--real or imaginary.

Changes in the technologies used in the latest generation of electronic fetal monitors has resulted generally in an improvement in the quality of the FHR data produced. However, in a number of instruments the use of inappropriate printers and signal processing has led to a degradation in the FHR trace. This may result in difficulties in interpretation of the data thereby putting the compromised fetus at risk. This paper discusses the factors which affect the interpretation of the data, such as signal detection and rejection of noise, errors due to the signal processing and rate determination, and the effect of the chart recorder on the presentation of the data. Finally information is given about the UK Departments of Health evaluation programme for electronic fetal monitors (cardiotocographs).