Fetal acidaemia, the cardiotocograph and the T/QRS ratio of the fetal ECG in labour.
OBJECTIVE
To relate the T/QRS ratio of the fetal electrocardiogram (ECG) to the cardiotocogram (CTG) and fetal pH during labour.


METHODS
Prospective data collection from selected monitored labours.


METHODS
A postgraduate teaching hospital delivery suite.


METHODS
113 women in labour at term.


METHODS
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 acidemia.


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 less than 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 less than 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.


CONCLUSIONS
A raised T/QRS ratio (greater than 0.28) had a considerably lower detection rate for fetal acidaemia during labour than a pathological CTG.
Maclachlan
N A
NA
Institute of Obstetrics and Gynaecology, Royal Postgraduate Medical School, University of London.
Spencer
J A
JA
Harding
K
K
Arulkumaran
S
S
D000138:Acidosis / Q000097:blood / Q000503:physiopathology*; D000328:Adult; D015148:Cardiotocography; D004562:Electrocardiography; D005260:Female; D005312:Fetal Blood / Q000502:physiology; D005315:Fetal Diseases / Q000097:blood / Q000503:physiopathology*; D006340:Heart Rate, Fetal; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007743:Labor, Obstetric / Q000097:blood; D011247:Pregnancy; D014469:Umbilical Arteries / Q000503:physiopathology