Types of intrapartum hypoxia on the cardiotocograph (CTG): do they have any relationship with the type of brain injury in the MRI scan in term babies?

Abstract

Electronic foetal monitoring using cardiotocography is aimed at the timely recognition and management of foetal hypoxia. The primary objective of this study was to examine whether a relationship exists between the types of foetal hypoxia (acute, subacute, evolving, chronic), as identified on cardiotocography and the nature of hypoxic ischaemic encephalopathy, as observed on MRI scans after birth. We conducted a retrospective study of 16 babies born (out of 52,187 births) at St George’s Hospital in London during 2006–2017 with a postnatal diagnosis of HIE. Of the 16 babies, only 11 had both MRI scans and CTG traces available. Of those, 9 showed evidence of intrapartum hypoxia on CTG, but only 6 demonstrated evidence of HIE on MRI. Those with acute hypoxia showed abnormalities in the basal ganglia and thalami. A gradually evolving hypoxia or subacute hypoxia was associated with lesions in myelination and cerebral cortex.

Impact Statement

• What is already known on this subject? It has been reported that inter-observer agreement for CTG interpretation is low (30%) when pattern recognition based guidelines are used (Rhöse et al. 2014; Reif et al. 2016), even amongst ‘experts’ (Hruban et al. 2015). Furthermore, it has been shown that CTG traces do not reliably predict neonatal encephalopathy (Spencer et al. 1997).

• What do the results of this study add? Our study indicates that if ‘types of intrapartum hypoxia’ are used for interpretation, then inter-observer agreement increases to 81%, from the reported 30% when traces are classified into ‘normal, suspicious and pathological’ using guidelines based on ‘pattern recognition’. Furthermore, our study shows a good correlation between the type of intrapartum hypoxia observed on CTG trace and the nature of injury observed on the MRI.

• What are the implications of these findings for clinical practise and/or further research? Improving inter-observer agreement of CTGs with the use of pattern recognition in combination with the good correlation to MRI scan findings ultimately leads to better management and post-natal outcomes. This is evidenced by the fact that after the introduction of physiology-based CTG interpretation and mandatory competency testing on CTG interpretation for all staff in 2010, St. George’s Maternity Unit has half the nationally reported rate of cerebral palsy.

Keywords:

• CTG
• foetal monitoring
• hypoxic ischaemic encephalopathy
• MRI
• APGAR scores
• cord gases

Acknowledgements

Swetha Yatham and Edwin Chandraharan conceived the concept and designed the study. Virginia Whelehan and Abigail Archer maintained the prospective database of CTG traces and perinatal outcomes. Swetha Yatham reviewed all the CTG traces and MRI Scans and Edwin Chandraharan double checked the CTG traces to ensure inter-observer agreement. Swetha Yatham analysed the data. Swetha Yatham and Edwin Chandraharan co-wrote the manuscript and all authors reviewed and edited the manuscript.

Disclosure statement

Swetha S. Yatham, Virginia Whelehan, and Abigail Archer report no conflicts of interest. Edwin Chandraharan conducts several Masterclasses on CTG and foetal ECG in the UK, Europe, Asia and Australia and is the co-organiser of the Intrapartum Foetal Surveillance Course at the Royal College of Obstetricians and Gynaecologists (RCOG) and Foetal Monitoring Courses at St George’s University of London. Some of the hospitals and organisations who have organised these Masterclasses have received funding from Philips, Neoventa, Euroking, Cardiac Services and several Law Firms. However, EC does not have any financial or managerial interests in any medical device or pharmaceutical industry. He was a member of the Editorial Board for NHS e-learning on CTG and a Course lead for the Baby Lifeline CTG Masterclasses. He was a member of the guideline development group which produced the international FIGO Guidelines on CTG (2015) and he is on the Editorial Board of physiological-ctg.com.