Fetal ECG during labour: a presentation of a microprocessor system.

Changes in the ST waveform of the fetal ECG have been detected in 47 term deliveries with vertex presentations using a specially developed microprocessor-based system for on-line recording of T wave amplitude. The T wave was quantified by the T/QRS ratio. The recording included one scalp electrode for exploration and a maternal skin electrode as reference. Signal quality allowed optimal ST waveform assessment in 89% of the cases. The degree of perinatal asphyxia was judged from cord artery acid-base status and the neonatal outcome. In completely normal fetuses at term the mean T/QRS ratio was 0.148 with a standard deviation of 0.048. With this basic information we can proceed in the investigation of the T/QRS ratio as a means for fetal surveillance.