Improving intrapartum surveillance: an individualised T/QRS ratio?

OBJECTIVES

To test the T/QRS ratio of the fetal electrocardiogram for normal distribution and assess the potential value of an individualised T/QRS ratio threshold to depict abnormality in the detection of fetal compromise during labour.

STUDY DESIGN

A retrospective analysis of twenty intrapartum fetal electrocardiogram recordings obtained on the labour ward of the Queen's Medical Centre, Nottingham.

RESULTS

In two of the twenty cases the T/QRS ratio was normally distributed. An increase in the T/QRS ratio over the 97.5th and 99.5th centile for 2 consecutive minutes, calculated on an individual basis, would appear to discriminate best between biochemically compromised and non-compromised fetuses. In no case was the T/QRS ratio seen to exceed 0.25 for periods previously described to be related to poor outcome.

CONCLUSION

T/QRS ratio changes with individually calculated criteria for abnormality may be of benefit in the detection of fetal compromise but the effect on the intervention rate remains to be established. The use of an absolute threshold for T/QRS ratio abnormality which is based on the assumption of a normal distribution needs to be viewed with caution.