A recognised issue with CTG monitoring is the risk that what you think you are seeing is in fact not the fetus’s heart rate, it is the woman’s (Stamplija, et al., 2012). This can lead to failure to intervene appropriately in labour when there is a significantly abnormal fetal heart rate that isn’t being recorded. Using a fetal spiral (or scalp) electrode (FSE) can help to reduce the chance of picking up the wrong heart rate. Unfortunately, FSEs are invasive in nature (requiring a vaginal examination, for the membranes to be or have been ruptured, and involve a thin wire being screwed through the fetal skin to obtain contact). Their use carries some risks relating to their invasive nature (Fick, et al., 2021; Kawakita, et al., 2016), and while these complications are uncommon it would be nice to avoid them altogether.
Technology developers have been working on ways to monitor the electrical signal from the fetal heart rate through the pregnant woman’s abdomen as a means to solve both these problems (Lempersz, et al., 2020). While the issues relating to invasiveness are addressed well by these systems, they have continued to have issues with their ability to reliably detect the fetal heart rate at all times. New research has just been published looking at a system combining both trans abdominal fetal ECG monitoring with phonocardiocography – that is simply recording the sound the fetal heart rate makes with a microphone placed on the woman’s abdomen (Faisant, et al., 2022). The inputs from both ways of detecting the fetal heart beats were combined to try to increase the amount of time when the heart rate could be reliably determined.
In this particular trial, the authors used both traditional CTG monitoring (Doppler ultrasound for the heart rate and an external tocograph for the contractions) plus their new system at the same time (that was a lot of gadgets on the one tummy!). This meant they could compare the signal quality from the traditional CTG with their new multi-modal approach simultaneously to see how they both performed. Forty women, all more than 37 weeks pregnant and none of them in labour, had a 30 minute recording period with the monitoring equipment. 38 useable traces were analysed.
The researchers were able to obtain a reliable heart rate with the CTG for 93% of the duration of the trace. In 25 traces the fetal ECG was sufficient on its own and in 30 the phonocardiogram was enough on its own. In 35 of the 38 tracings the combination of fetal ECG and phonocardiogram was able to produce an accurate fetal heart for the duration of the trace. Clearly the combination of both was better. The authors did record a period of maternal heart rate recording on a CTG when the multimodal trace was able to continue to accurately record the fetal heart rate, highlighting the potential usefulness of this approach once it has been fine tuned.
There remains much work to be done to bring new technology solutions to old CTG problems to the market and to demonstrate that they do indeed work as promised. It would be nice to one day have a system that didn’t require invasive procedures to apply, didn’t limit movement or the option of using a shower or a bath during labour, and reliably recorded the fetal heart rate. It would of course, be even better if such monitoring improved perinatal outcomes without harming women, but I am not confident that we will ever do the research needed to answer that particular question.
References
Faisant, M. C., Fontecave-Jallon, J., Genoux, B., Rivet, B., Dia, N., Resendiz, M., Riethmuller, D., Equy, V., & Hoffmann, P. (2022, Jun 8). Non-invasive fetal monitoring: Fetal Heart Rate multimodal estimation from abdominal electrocardiography and phonocardiography. Journal of Gynecology Obstetrics and Human Reproduction, in press, 102421. https://doi.org/10.1016/j.jogoh.2022.102421
Fick, T., & Woerdeman, P. A. (2021, Apr 6). Neonatal brain abscess development following fetal scalp electrode placement: a rare complication. Child’s Nervous System, 38(1), 199-202. https://doi.org/10.1007/s00381-021-05150-7
Kawakita, T., Reddy, U. M., Landy, H. J., Iqbal, S. N., Huang, C.-C., & Grantz, K. L. (2016, Oct). Neonatal complications associated with use of fetal scalp electrode: a retrospective study. BJOG: An International Journal of Obstetrics and Gynaecology, 123(11), 1797-1803. https://doi.org/10.1111/1471-0528.13817
Lempersz, C., Noben, L., de Vries, B., van Laar, J., Westerhuis, M. E. M. H., & Oei, s. (2020). The noninvasive fetal electrocardiogram during labor: A review of the literature. Obstetrical & Gynecological Survey, 75(6), 369-380.
Stampalija, T., Signaroldi, M., Mastroianni, C., Rosti, E., Signorelli, V., Casati D., & Ferrazzi, E.M. (2012). Fetal and maternal heart rate confusion during intra-partum monitoring: comparison of trans-abdominal fetal electrocardiogram and Doppler telemetry. Journal of Maternal-Fetal & Neonatal Medicine, 25(8), 1517-1520. 10.3109/14767058.2011.636090
Categories: antenatal CTG, CTG, EFM, New research
Tags: fetal ECG, fetal electrocardiography, fetal scalp electrode, Fetal spiral electrode, FSE, maternal heart rate, phonocardiography
Birth Small Talk 