I keep a close eye on any new research about fetal heart rate monitoring as it is published (thanks Google Scholar alerts). There is a certain genre of research that appears quite often and is used by CTG proponents to argue that CTG monitoring is effective. This genre relates to research confirming that certain fetal heart rate patterns seen on the CTG are associated with worse outcomes for the fetus and baby. Here’s a few from my collection (note that I’m not criticising these researchers or the quality of their work – this is all great science):
- Ray and Ray, 2017 – documented that cord blood acidosis was more common when there had been abnormal CTG patterns (type II and III according to the NICHD guideline)
- Rao, et al., 2022 – found that cord blood acidosis was more common when the CTG had been suspicious or pathological (FIGO guideline)
- Lovers, et al., 2022 – babies born with severe compromise more commonly had early labour CTG patterns with fetal tachycardia, reduced short- or long-term variability, absence of accelerations, or the presence of decelerations (Oxford system computer interpretation)
- Reynolds, et al., 2022 – babies with neonatal encephalopathy were more likely to have abnormal CTG traces (NICE guideline)
Here’s the thing though. The way that CTG monitoring is meant to work is by detecting changes in the fetal heart rate early so that clinicians can take action that prevents the development of a problem in the baby. What these studies all show is that this goal is not being achieved.
Each of these studies was done in a setting where CTG monitoring was used for clinical decision making. The health care professionals providing care to labouring women could see the CTG trace and were using it to guide their recommendations to women. If CTG monitoring were working as promised, then the association with poor outcomes should be very weak or absent in these populations as CTG use would prevent these outcomes. Sure, you might argue that acidosis represents a “just in time” rescue rather than a poor outcome per se, but studies linking CTG patterns with neonatal compromise and encephalopathy reinforce that our current clinical practices with CTG monitoring don’t work as advertised.
How are we to interpret these findings then? Potentially they might mean one or more of the following:
- There are system-wide barriers preventing appropriate and timely responses to abnormal CTG traces. While this might be possible, it seems unlikely given the diversity of research sites producing the types of findings I am referring to here. Surely not all places where CTG monitoring is in use are struggling to respond to abnormal traces appropriately. Ethnographic research approaches would be useful to understand what is happening in the time from when the CTG becomes abnormal to when birth occurs to identify potential areas for improvement.
- Researchers might yet be able to correctly identify fetal heart rate patterns that indicate when the fetus shifts from compensating to labour processes to being harmed, when this harm is still reversible. Basic physiological research helps here (sorry sheep, this isn’t going to be good for you). Another option is to generate a CTG recording but not use it in labour management so that outcomes relate strongly to the CTG pattern and not to the care provided in response to the pattern. This is unlikely to make it past an ethics committee.
- Some of the practices commonly used around birth might be operating as confounding factors. For example, credible concerns have been raised that early cord clamping to facilitate neonatal resuscitation and the collection of cord blood gas samples may contribute to haemodynamic instability with the potential for neurological injury in susceptible infants (Asfour & Bewley, 2010). These practices are likely to be used when the CTG is considered abnormal. We need to look critically at what we are actually doing adjacent to CTG use and research it.
Let’s stop ignoring the elephant in the room. There is little demonstrable proof that CTG monitoring provides any benefit to the fetus or newborn. While researchers can do whatever (ethical) research they want, my preference would be that we channel funds, time, and energy into investigating options that might actually work.
Asfour, V., & Bewley, S. (2010). Might measuring cord pH in itself affect outcome? British Medical Journal, 341. doi:https://doi.org/10.1136/bmj.c4440
Lovers, A. A. K., Ugwumadu, A., & Georgieva, A. (2022). Cardiotocography and clinical risk factors in early term labor: A retrospective cohort study using computerized analysis with Oxford system. Frontiers in Pediatrics, 10, 784439. https://doi.org/10.3389/fped.2022.784439
Rao, S., Jain, H., Suneel, A., Shivananda, R., & Vasudeva, A. (2022). Correlation between intrapartum cardiotocograph findings and cord blood pH in term and preterm labours. Current Women’s Health Reviews, 18(3), 120-128. https://doi.org/10.2174/1573404817666210811124304
Ray, C., & Ray, A. (2017). Intrapartum cardiotocography and its correlation with umbilical cord blood pH in term pregnancies: a prospective study. International Journal of Reproduction, Contraception, Obstetrics and Gynecology, 6(7), 2745-2752. https://doi.org/10.18203/2320-1770.ijrcog20172555
Reynolds, A. J., Murray, M. L., Geary, M. P., Ater, S. B., & Hayes, B. C. (2022). Fetal heart rate patterns in labor and the risk of neonatal encephalopathy: A case control study. European Journal of Obstetrics & Gynecology and Reproductive Biology, 273, 69-74. https://doi.org/10.1016/j.ejogrb.2022.04.021