BirthSmallTalk is two and a half years old, with over 150 posts. The last few months have seen a bunch of new people join me. (Hello! And thank you for dropping by!) I’ve decided it is time to go back to earlier posts to refresh and update them, and have given the entire blog a fresh look. This is week three of a six week plan to revisit posts covering basic concepts and background information to help understand what is going on with fetal heart rate monitoring.
Last week I shared a post setting out the basics about CTG monitoring. This time I’m going to do the same for intermittent auscultation, often referred to as IA. Auscultation means to listen to something. Intermittent auscultation typically refers to listening to the fetal heart on a regular basis during the course of a woman’s labour. There is no universal agreement about how long to listen or how often this should occur, and no research evidence to help make recommendations about this. Most professional guidelines suggest something along the lines of listening for at least 60 seconds every 15 to 30 minutes, and more often during the pushing stage, usually but not always in between contractions.
The most common tool used for intermittent auscultation is a handheld fetal Doppler: a device that throws an ultrasound pulse into the tissues over which it is placed, then senses the returning echo of this pulse. By measuring the Doppler shift in the reflected ultrasound wave, it is possible to detect movement under the sensor, such as the fetal heart, or blood moving through a large blood vessel. To make it easy for human brains, this data is converted into an audible signal. Dopplers have become so commonplace that we now take for granted the sound that comes out of the speakers as a true recording of sound generated by the fetal heart. It is important to remember it is actually a heavily modified sound generated by technology.
There are ways to hear the actual sound of the fetal heart. The simplest way to do this is to put a listening ear directly onto the skin of the pregnant woman, over where the fetal chest is located. This is pretty tricky in a clinical situation, so devices to place some distance between the woman and the listener have been created. The Pinard (the instrument in the picture above) or De Lee stethoscope are the most commonly used, and regular stethoscopes also do the job. Each of these does require a bit more skill and practice to master than a Doppler does, and they won’t detect the fetal heart as early in pregnancy. The big advantage of these direct approaches is there is no possibility of the technology misleading you about what is really happening, and no theoretical concern about potential harms from the Doppler energy field.
Intermittent auscultation is NOT not being monitored
I often hear people say, or see it written, that someone is “not being monitored” when intermittent auscultation rather than CTG monitoring is being used. We need to be really careful about using this language. Intermittent auscultation IS fetal heart rate monitoring, in the same way that CTG use is fetal heart rate monitoring. Being a bit sloppy in the use of terminology helps to reinforce the (incorrect) belief that intermittent auscultation is an inadequate form of fetal heart rate monitoring. I challenge you to be precise in the terminology you use in practice, including when you are documenting in records.
The other potential confusion is the use of the term “intermittent monitoring”. This refers to the intermittent use of CTG monitoring during labour, for example using the CTG machine for twenty minutes every two hours. This is not the same as intermittent auscultation, and there is very little research comparing intermittent CTG monitoring with continuous CTG monitoring, and none has compared it with intermittent auscultation.
How to do intermittent auscultation well
Most high-income countries require maternity clinicians who work with women during labour to attend regular courses on the use and interpretation of CTG monitoring. I’ve been to more than a few during my time – but I have never been to an education session where there was a specific focus on how to use and interpret intermittent auscultation. (If you have, I’d love to hear about it in the comments!) This lack of education contributes to an unease about intermittent auscultation as an appropriate and justifiable option for fetal heart rate monitoring in labour.
The best approach I have come across is Intelligent Structured Intermittent Auscultation or ISIA, as outlined by midwives Robyn Maude, Joan Skinner, and Marilyn Foureur in 2016 (though I disagree with their assumption intermittent auscultation is only appropriate for women considered as low risk). The specifics are set out in their paper (find it on the reference list below), so I won’t repeat them here. What is important is to keep in mind that simply counting the number of beats per minute and writing it down is insufficient information to answer the question of whether the fetus is well at a given point in time.
Have we lost vital knowledge?
Years ago, I sat in my garden with two American midwives, Gail Hart and Patricia Edmonds, each with a lifetime of experience providing care to women in out of hospital settings. I asked them what they did during labour to assess fetal wellbeing. They described how as well as listening for changes in the rate and pattern of the fetal heart, there are also subtle changes in the sound of the heart – sounds that can only be appreciated with a well-trained ear listening directly to the fetus. Other researchers have more recently captured this same knowledge (Engelhart et al., 2022). Patricia has since died. It makes me profoundly sad to contemplate how a lack of respect given to knowledge generated by women outside of the obstetric paradigm, and our obsession with technological tools, has brought us to a place where knowledge about intermittent auscultation without using a Doppler is almost lost to us.
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References
Engelhart, C. H., Nilsen, A. B. V., Pay, A. S. D., Maude, R., Kaasen, A., & Blix, E. (2022). Practice, skills and experience with the Pinard stethoscope for intrapartum foetal monitoring: Focus group interviews with Norwegian midwives. Midwifery, 108, 103288. https://doi.org/10.1016/j.midw.2022.103288
Maude, R. M., Skinner, J. P., & Foureur, M. J. (2016). Putting intelligent structured intermittent auscultation (ISIA) into practice. Women and Birth, 29(3), 285-292. doi:10.1016/j.wombi.2015.12.001
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