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

Abstract

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.

Linear analysis of fetal magnetocardiogram recordings in normal pregnancies at various gestational ages

“…It shows higher signal to noise ratio, reduces the maternal interference compared to FECG, and the electrically insulating properties of vernix caseosa have no apparent effect on it (Pardi et al, 1984;Van Oosterom et al, 1990;Quinn et al, 1994;Crowe et al, 1995;Newbold et al, 1995). Magnetic signals from the fetal heart are relatively unaffected by the poor conductivity of the surrounding tissues and the maternal heart and fall off rapidly with source-todetector distance.…”

Fetal magnetocardiogram recordings and power spectra analysis in biomagnetic arrhythmic signals

“…In addition, the amplitudes of the fetal heart signal diminish from 27 to 35 weeks' gestation because the vernix caseosa insulates the fetal skin (Oostendorp et al, 1989;Van Leewuen et al, 1995;Newbold et al, 1995). The cardiotocograph is based on the Doppler-shift of the ultrasound signal and gives a tachogram based on the repetition of these signals but it does not register irregular beats.…”