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The problem – learn more

In 1968 a new technology called cardiotocography (CTG) was introduced into clinical practice to monitor the fetal heart rate during labour. The aim was to recognise the onset of fetal compromise so that timely intervention could be undertaken to avoid hypoxic-ischaemic encephalopathy (HIE) or perinatal deaths. The CTG represents a continuous graphic record of the fetal heart rate (Cardio) and ongoing uterine contractions (Toco).

Unfortunately, CTG was introduced into clinical practice without any preceding, robust case-controlled studies or randomised controlled studies. Therefore, since its inception, CTG interpretation has heavily relied on “expert” opinions, which had crept into several national and international guidelines. It is noteworthy that unlike the adult ECG which has a consistent and of analysis of the waveforms across the world, there are more than 20 different Guidelines for the interpretation of CTGs [1-7]. These different national and different guidelines not only have different terminologies and categorisation, but they differ significantly with regard to thresholds for intervention for the same CTG feature, even though human fetuses have the same physiological responses across the world. This approach has not only resulted in significant inter- and intra-observer variation in the classification of CTG, but also significant variation in maternal and perinatal outcomes [8-17].

After 50 years of clinical use, this technology has become the “gold standard” for intrapartum assessment of fetuses, who are considered to be at high-risk of intrapartum hypoxic insult. The most important clinical decisions made by obstetricians and midwives, which may have a life-long impact on mothers, their babies and families during a delivery often rely on the analysis of the CTG trace. Current evidence from Cochrane Systematic Review (2017) suggests that, despite its ubiquitous use, the CTG has NOT decreased the rate of neonatal death, or cerebral palsy, but has contributed to a tremendous increase of caesarean sections and operative vaginal births (forceps and vacuum) [18]. The only potential benefit is the reduction of neonatal seizures, but this is not associated with any improvement in long-term neurological outcomes in children. Therefore, the continued use of CTG in clinical practice using the current tools of CTG interpretation based on “pattern-recognition” which predisposes to human error has been recently questioned [19-23]

Current limitations and challenges with regard to CTG interpretation

  • many different classification systems exist causing confusion, with poor scientific evidence to support their use
  • a lack of reproducibility with a 30% inter observer variability, which means that that one in 3 doctors and/ or midwives can make a different diagnosis when analysing the same CTG trace, which would lead to significant variation in maternal (emergency caesarean section rates) and perinatal (hypoxic-ischaemic encephalopathy leading to cerebral palsy or deaths) outcomes.
  • Approximately 30% intra-observer variability where a doctor or a midwife makes a different diagnosis of himself/herself when analysing the same CTG at two different times. Scientific evidence suggests that even “CTG experts” change their own opinion and change their classification of CTG when they are made aware of the perinatal outcomes.
  • a lack of accuracy, although it was shown in 1971 that the false positive rate of CTG trace was 60% when a pH of 7.20 was used to define metabolic acidosis [24], if the correct cut off of 7.0 is used, in contemporary obstetric practice, the false positive rate could be > 90% [25, 26]. This indicates that > 90% of emergency caesarean sections and operative vaginal births performed for “CTG abnormalities” are potentially unnecessary.

Furthermore, missed fetal hypoxia due to CTG misinterpretation can lead to birth asphyxia with babies’ death or life long disabilities, leading to both human and financial costs. In fact, CTG misinterpretation contributes to significant medical malpractice claims [27-29] has a strong impact on the medical malpractice insurance.

Errors made during CTG analysis

  • represents 70% of the motives of litigations in obstetrics
  • drives to the highest compensations in medicine by insurers up to 15 million euros per case in Europe and 1 billion euro/year just for UK
  • is the main reason of high cost of OB/GYN Medical Malpractice Insurance: from 30 thousand euros per year per private specialist in France to 200 thousand dollars in USA.
  • CTG misinterpretation has also an enormous Human Costs to babies, mothers, families [30] as well as to obstetricians and midwives who have been involved in an adverse event due to CTG misinterpretation contributing to medico-legal claims [31, 32].


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