Oxford Centre for Fetal Monitoring Technologies

 

The Oxford Centre for Fetal Monitoring Technologies was born in the early 2012 as a natural umbrella for the relevant work in the Nuffield Department of Obstetrics and Gynaecology spanning over 30 years. Observation of the fetal heart rate is the core of standard fetal monitoring both prior to and during labour. The beating of the baby's heart is displayed on a continuous paper strip, showing a graph that changes through time (time-series). Any contractions are also detected and displayed on a separate concurrent graph. In labour, the responce of the fetal heart rate to contractions is of particular importance.

Monitoring during labour (Intrapartum)

During birth, the stress of contractions and descent through the birth canal can reduce a baby’s oxygen supply. In the UK alone, every year, about 100 healthy babies die[1] and about 1,100 sustain brain injury[2] during labour at term. Nearly 50% of the NHS litigation bill is due to obstetric claims (£3.1bn in 2000-10), most of which relate to shortcomings in labour management and CTG interpretation[3].

To identify the fetus at risk and prevent birth asphyxia, the baby’s heart beat is electronically recorded during labour on a paper strip (Cardiotocogram, CTG). The complicated patterns are assessed by eye, which is error-prone and unreliable. Even experts disagree with each other or with themselves when reviewing the same trace at different times. Such uncertainty causes ‘fail-safe’ decisions and many unneeded Caesarean sections. We estimate that about 36,000 unnecessary emergency deliveries (Caesareans and instrumental vaginal deliveries) are performed each year in the UK.

We will design a new diagnostic system, using objective computer analysis to assist interpretation of the labour CTGs. We have saved the electronic CTGs of nearly 60,000 babies with relevant clinical details. We can now study fetal health in relation to the baby’s CTGs and grade the associated risks by statistical analysis. Although this analysis is complex, because CTGs change as labour advances or with events such as epidural use, the unique size of our database makes the analysis very powerful.

We have already completed substantial preliminary work: we have derived from the data a first prototype of a diagnostic system (OxSys) that uses computer algorithms to reliably interpret the CTG. Despite its simplicity, OxSys compares favourably to clinical assessment (in a large retrospective cohort), with higher sensitivity for compromise (37.6% vs. 32.2%,p< 0.05) and lower intervention rate in normals (14.5% vs. 16.4%,p< 0.001). But there is a major scope for improvement, and in the coming years, we will refine OxSys to achieve substantially higher sensitivity and lower false positive rate on the data. We will achieve this by developing further OxSys's computer methods and establishing the role of additional clinical confounders, including new biomarkers for fetal growth and placental problems. Large testing sets of 'unseen' data will be used before prospective clinical testing.

Our system will identify the CTG patterns that matter most for the baby. Eventually, the labour experiences of over 100,000 women will be distilled into the memory of a computerised system to aid recognition of impending asphyxia, at the bedside. Such a system does not yet exist.

[1] Perinatal Mortality 2008, Centre for Maternal and Child Enquiries, United Kingdom, London (2010).
[2] J.J. Kurinczuk, M. White-Koning, N. Badawi. Epidemiology of neonatal encephalopathy and hypoxic-ischaemic encephalopathy Early Hum Dev 86, 329-38 (2010).
[3] The NHS Litigation Authority. Ten years of maternity claims: an analysis of NHS Litigation Authority data (2012).

Monitoring before labour (Antepartum)
Electronic fetal heart rate monitoring was introduced in 1966 for use in labour. The technique was then successfully applied to monitoring the distressed fetus before labour. It was quickly appreciated that it generated errors due to the unstandardised process of visual assessment of complex patterns. This led to the development of the Oxford Dawes Redman computerised system for objective numerical recognition of important abnormal features. It is now marketed by Huntleigh Healthcare. The system has been developed and validated on nearly 100,000 traces linked to clinical outcome data. The system is constantly being upgraded and a new refined version is being currently implemented by Huntleigh Healthcare, to be released soon.

Pardey J, Moulden M, Redman CW. A computer system for the numerical analysis of nonstress tests. Am J Obstet Gynecol 2002;186:1095-1103

The CTG is displayed on a paper strip