The effect of uterine contractions on the T/QRS ratio of the fetal electrocardiogram.

The aim of this study was to establish whether the T/QRS ratio of the fetal electrocardiogram (ECG) was influenced by uterine contractions. Data was collected from 55 women during labour using a purpose built computer which also measured background noise. The T/QRS ratio was measured on individual complexes and the measurements averaged. Measurements made during periods of excessive noise were excluded. The average T/QRS ratio during contractions showed a small but significant increase of 1.02% (principally in the second half of the contraction). The significance of this small increase is uncertain and for most fetuses the ratio would remain in the normal range during contractions. The higher T/QRS ratios, recorded in the noisy records, draw attention to the importance of accounting for this problem when fetal ECG data are reported.