Fetal acidaemia, the cardiotocograph and the T/QRS ratio of the fetal ECG in labour


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Objective To relate the T/QRS ratio of the fetal electrocardiogram (ECG) to the cardiotocogram (CTG) and fetal pH during labour. Design Prospective data collection from selected monitored labours. Setting A postgraduate teaching hospital delivery suite. Subjects 113 women in labour at term. Main outcome measures Correlation of fetal T/QRS ratio values with pH values at the time of fetal blood sampling and at birth (umbilical artery blood). Comparison of the predictive values of raised T/QRS ratio and a pathological CTG for fetal acidaemia. Results Complete data sufficient for analysis was available for 51 fetal scalp blood samples and 93 umbilical artery pH samples. The median (range) of T/QRS ratio values before birth of 88 babies not requiring admission to the neonatal unit was 0.13 (0.00–0.32) with a 97.5th centile value of 0.28. T/QRS ratios did not correlate with fetal scalp pH values. Fetal scalp acidaemia (pH<7.20) was detected with rates of 50 and 13% respectively by a pathological CTG and by a T/QRS ratio above 0.28, the positive predictive values being 40% and 50%, respectively. There was a significant correlation between increasing T/QRS ratio and falling pH. Detection rates (sensitivities) for umbilical artery acidaemia (pH<7.12) were 76% and 29% whereas positive predictive values were 38% and 71% respectively for a pathological CTG and a T/QRS ratio above 0.28. Conclusion A raised T/QRS ratio (<0.28) had a considerably lower detection rate for fetal acidaemia during labour than a pathological CTG.

Original languageEnglish
Pages (from-to)26-31
Number of pages6
JournalBJOG: An International Journal of Obstetrics & Gynaecology
Issue number1
Publication statusPublished - 1992


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