Mon, 30 Jul 2018
This article originally appeared in the AvMA Lawyers Service Newsletter (June 2018)
Cardiotocography traces form a central piece of documentary evidence in litigation related to adverse perinatal outcomes, which are alleged to have arisen due to events that took place during the labour and/or delivery of the baby. Cardiotocography is therefore an important element to get to grips with for any practitioner when working on birth injury cases. Errors in electronic fetal heart rate monitoring or cardiotocography are a common theme in such cases with injuries to the baby including cerebral palsy, stillbirth and scarring and injuries to the mother including damage to the mother’s perineum or vagina resulting in disability which limits sexual intercourse, lack of control of bladder/bowel function and of course psychological or psychiatric sequelae. A recent review by NHS Resolution in September 2017 found that 32 out of the 50 cerebral palsy cases looked at, involved errors of cardiotocography interpretation. This article is a beginner’s guide to cardiotocography for application in medical negligence cases.
What is cardiotocography?
Cardiotocography is a technical means of recording the fetal heartbeat and the uterine contractions during pregnancy and intrapartum. The cardiotocography recording is produced in the form of a graphical trace and is important to midwives and obstetricians when evaluating in real time whether there is fetal compromise or not. The upper channel [cardiograph] represents the fetal heart and the lower [tocograph] records the frequency of uterine contractions [not strength]. The cardiograph may be recorded by an ultrasound signal through the mother’s abdominal wall or via an electrode attached to the baby’s scalp, so called a fetal scalp electrode. The tocograph is produced by an external tocodynamometer placed at the fundus of the uterus to measure the frequency of the contractions. Internal monitoring of the fetal heart rate by use of a fetal scalp electrode provides a more accurate and consistent transmission of the fetal heart rate than external monitoring because factors such as movement do not affect it. Internal monitoring may be used when external monitoring of the fetal heart rate is inadequate, or closer surveillance is needed. The current relevant guidance on cardiotocography is detailed within NICE Clinical Guideline CG190 on Intrapartum Care . The use of a standard format in the guidance to interpret and respond to fetal heart rate, serves to facilitate safety in clinical practice and provide more clarity in legal cases. Practitioners should refer to the relevant guidance in place at the time of the alleged negligence when considering matters of negligence. More about the guidance below.
Cardiotocography is most commonly used in the third trimester and during labour. Its purpose is to monitor fetal wellbeing and allow detection of fetal distress which usually means the fetus is hypoxic or anoxic. [deprivation of adequate oxygen supply]. All pregnancies, regardless of risk category, need effective monitoring: only 1 in 5 claims for cardiotocography interpretation involve a high-risk pregnancy. An abnormal CTG trace indicates the need for more invasive investigations and potentially emergency Caesarean section. Appropriate interpretation of CTG traces is therefore fundamental if there is to be a reduction in the number of baby deaths and/or serious injury. The relevance to medical negligence work will be patently clear.
Interpretation of CTG traces is a very complex subject of which experts frequently differ. As a consequence, even the most superficial review would be beyond the scope of this article.
Lawyers are advised to leave the interpretation of CTG traces to their instructed experts. Experts will be looking at the traces when considering the standard of care provided and whether there were signs of fetal compromise or not at a certain time which should have prompted earlier or later action in relation to delivery. Below is only a highlevel summary of the main features.
Tables 10 and 11 of the current NICE guideline, CG190 provide guidance on the interpretation of CTG traces and the reader is referred to the whole of section 10 for further information.
The four main features used to assess a CTG trace are:
- Baseline fetal heart rate
- Baseline variability
- Fetal heart rate acceleration
- Fetal heart rate decelerations
Generally, accelerations are a sign the baby is healthy. The appropriate response to a uterine contraction is an increase in the fetal heart rate [acceleration]. The baseline rate is the average heart rate of the fetus in a 10-minute window. The normal fetal heart rate is between 110 – 150bpm. A baseline variation of less than 5 bpm is an abnormal sign! Variability greater than 5bpm is generally a sign that the baby is healthy.
Decelerations are an abrupt decrease in the baseline fetal heart rate by 15 bpm for 15 seconds or more. There are different kinds of decelerations, [early, variable, late and prolonged] each with varying significance. The baseline rate, variability and decelerations are categorised as normal/reassuring, non-reassuring and abnormal as per Table 10. Table 11 provides the management approach subject to the interpretation and categorisation of the features of the CTG trace. When there is a single prolonged deceleration or bradycardia with a baseline below 100 bpm persisting for 3 minutes or more, the CTG is classed as abnormal and warrants the need for urgent intervention.
When instructing experts, practitioners should ensure that the full clinical picture is taken into account, as clinicians must do in practice. Such factors include the presence of meconium stained liquor in the amniotic fluid; delay during labour, abnormal fetal position and whether there is acidosis following blood gas analysis of a fetal blood sample. Furthermore, whether the pregnancy was high or low risk will also be relevant. Such factors will assist when trying to understand what the picture was at the time of the index events and what the clinicians knew at that time when providing treatment and care.
Uncertainty is part and parcel of CTG traces and therefore the scope for error can make clinical negligence claims challenging. Traces have a high false positive rate and the transducer could be picking up the maternal heart rate instead of the fetal heart rate. Practitioners should try and draw out any potentially misleading features on the CTG traces with their experts in order to get a realistic snapshot of how a responsible body would have interpreted the CTG trace at the time. Intrauterine observation along with consideration of the full clinical picture is critical in determining whether or not breach of duty is established. The majority of birth injury cases incorporate similar allegations of negligence which broadly centre around the inability to interpret the CTG trace correctly, for example failure to identify bradycardia in time leading to delay in proceeding to caesarean section. In the ordinary case it is still necessary to show that the signs of foetal compromise could reasonably have been detected and that delivery could and should have been expedited. Casework will usually include analysis of the timings as to when fetal distress would have been identified by a reasonably competent midwife/obstetrician and at what time should certain steps/treatment have taken place. Conversely allegations relating to liability may be that the delivery was carried out too soon causing injury.
In the event breach of duty can be proved by a Claimant, it will still be necessary for the Claimant to prove on balance that the injury, be it cerebral palsy or otherwise would have been avoided if delivery was expedited at a certain time. Not only can breach of duty be a difficult hurdle to overcome in obstetric cases, but causation can also bring its challenges. The experts will need to consider what would have happened if the patient had been delivered at a certain time with appropriate management along with the likely cause of the injury actually suffered. In cerebral palsy cases, paediatric neurology expert evidence may be needed to identify the cause of brain damage which may have occurred in any event irrespective of any delay.
The doctor’s or midwife’s clinical notes are not sufficient; practitioners must consider the CTG traces themselves. Claimant lawyers will need to ensure they have the whole trace relating to the labour and delivery of the baby in any given case and that it is clear enough to be read. Practitioners should instruct their experts [obstetricians or midwives] to explain the trace in detail in their reports with reference to the relevant guidance in place at the time of the index events. Similarly, the Defendant clinicians’ witness statements in relation to the interpretation of the CTG trace must be cross referenced with the Claimant’s expert’s own interpretation of the trace. When preparing for trial, parties may wish to include a glossary of terms in the trial bundle to assist the Court with the technical medical concepts and practitioners should also consider enlarging the traces for trial in order to ensure they are as legible as possible reducing the scope for error.
Finally, cardiotocography despite its limitations and scope for error is here for the foreseeable future. There is not currently a more effective way of monitoring fetal wellbeing and therefore doctors, nurses and lawyers will need to continue to rely upon them and endeavour to interpret them.
Clinical Negligence Group
 Section 1.10, Clinical Guideline CG190. NICE CG190, Intrapartum Care: Care of healthy women and their babies during Childbirth. December 2014.
 Powers and Barton on Clinical Negligence, Bloomsbury Professional, 5th edition.
 Sections 1.12 and 1.13. NICE CG190, Intrapartum Care: Care of healthy women and their babies during Childbirth. December 2014.