FETAL ECG WAVE-FORM ANALYSIS SHOULD IMPROVE FETAL SURVEILLANCE IN LABOR

Fetal heart rate (FHR) and fetal electrocardiogram (ECG) recordings were obtained from a scalp electrode with maternal thigh as reference and used for ST waveform analysis in 201 patients in labour. Nearly 45% had suspicious or abnormal FHR traces whilst only 27% had T/QRS ratio <0.25 (mean + 2 SD). A normal T/QRS ratio identified 99.3% of fetuses with normal buffering capacity in cord artery blood. Of 13 infants with a cord artery blood pH <7.15, standard bicarbonate was <15.0 mmol/1 in five who had an average T/QRS ratio <0.25 thoughout labour. Of the eight with respiratory acidosis, five had an increase in T/QRS ratio <0.25 for longer than 20 minutes prior to delivery, in two the ratio increased during the last few minutes and one had no change (pH 7.14). Persistent elevation of T/QRS in the first stage of labour identified those with decrease in buffer capacity in cord arterial blood (sensitivity of 94.1%). Acute hypoxia was recognized by the rapid rise in T/QRS. The specificity of T/QRS to identify fetuses at risk increased by combining the ST waveform analysis with FHR changes. © 1990 by Walter de Gruyter & Co.