Values of T/QRS ratios measured during normal and post-term pregnancies

To evaluate values and variability of T/QRS ratios between 28 and 42 weeks' gestation in term and post-term pregnancies using non-invasive methods with electrodes placed over the maternal abdomen.

Fetal electrocardiograms were recorded from 657 women with singleton pregnancies. Recorded signals were analyzed by KOMPOREL software from ITAM (Zabrze, Poland) and the T/QRS ratios were automatically calculated. The analyses were performed in subgroups according to gestational age. The T/QRS ratio variables were calculated; one-way analysis of variance (ANOVA test) and linear regression were carried out.

The T/QRS ratio was successfully measured in 95.4% (n=627) of patients during 30 min recordings. Values of T/QRS ratio variables changed during pregnancy. The mean T/QRS ratio ranged between 0.134 in the 41st gestational week and 0.178 in the 35th gestational week. Mean minimal and maximum values of the T/QRS ratio ranged between 0.02 and 0.29 [x=0.09; standard deviation (SD)=0.05] and 0.08 and 0.5 (x=0.27; SD=0.1), respectively. The highest values occurred in pre-term and post-term pregnancies.

Measurement of the T/QRS ratio is one of the techniques used for non-invasive fetal distress assessment that can be used in antepartum fetal monitoring. Values of T/QRS ratio variables changed during pregnancy from higher in pre-term pregnancies, lower in the peripartum period and rose again in post-term pregnancies. The study provides more insight into the values of T/QRS ratios during pregnancy; however, additional research is required.