The electrical heart axis and ST events in fetal monitoring: A post-hoc analysis following a multicentre randomised controlled trial

PLoS One. 2017 Apr 14;12(4):e0175823. doi: 10.1371/journal.pone.0175823. eCollection 2017.


Objective: Reducing perinatal morbidity and mortality is one of the major challenges in modern health care. Analysing the ST segment of the fetal electrocardiogram was thought to be the breakthrough in fetal monitoring during labour. However, its implementation in clinical practice yields many false alarms and ST monitoring is highly dependent on cardiotocogram assessment, limiting its value for the prediction of fetal distress during labour. This study aims to evaluate the relation between physiological variations in the orientation of the fetal electrical heart axis and the occurrence of ST events.

Methods: A post-hoc analysis was performed following a multicentre randomised controlled trial, including 1097 patients from two participating centres. All women were monitored with ST analysis during labour. Cases of fetal metabolic acidosis, poor signal quality, missing blood gas analysis, and congenital heart disease were excluded. The orientation of the fetal electrical heart axis affects the height of the initial T/QRS baseline, and therefore the incidence of ST events. We grouped tracings with the same initial baseline T/QRS value. We depicted the number of ST events as a function of the initial baseline T/QRS value with a linear regression model.

Results: A significant increment of ST events was observed with increasing height of the initial T/QRS baseline, irrespective of the fetal condition; correlation coefficient 0.63, p<0.001. The most frequent T/QRS baseline is 0.12.

Conclusion: The orientation of the fetal electrical heart axis and accordingly the height of the initial T/QRS baseline should be taken into account in fetal monitoring with ST analysis.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial

MeSH terms

  • Adolescent
  • Adult
  • Cesarean Section
  • Electrocardiography
  • Female
  • Fetal Blood / chemistry
  • Fetal Diseases / physiopathology
  • Fetal Monitoring*
  • Gestational Age
  • Heart Rate, Fetal / physiology*
  • Humans
  • Hydrogen-Ion Concentration
  • Labor, Obstetric
  • Pregnancy
  • Young Adult

Grant support

This research was financially supported by Dutch Technology Foundation STW. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. Funding was received by RV.