Earlier this 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. IA 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 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.
The most common tool used for IA is a handheld fetal Doppler: a device which 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 that the sound that comes out of the speakers is a true recording of sound generated by the fetal heart. It is important to remember that 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 which place some distance between the woman and the listener have been created. The Pinard 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 that there is no possibility of the technology misleading you about what is really happening.
Intermittent auscultation is NOT not being monitored
I not infrequently hear people working in hospital birth environments say that a particular woman is “not being monitored” when IA rather than CTG monitoring is being used. This language also pops up in research literature, particularly in older research, where the comparison groups have been referred to as “monitored” and “unmonitored”. We need to be really careful about falling into a habit of misrepresenting the form of fetal monitoring being used. Intermittent auscultation IS fetal monitoring. Being a bit slipshod in the use of this terminology helps to reinforce the (incorrect) belief that IA is a less than appropriate option for fetal monitoring. I challenge you to be precise in the terminology that you use in practice, including when you are documenting in records.
The other potential confusion in language is the use of the term “intermittent monitoring”. This refers to the intermittent use of CTG monitoring during labour, for example using the CTG for twenty minutes every two hours. This is not the same as IA, and there is very little research which has compared intermittent CTG monitoring with continuous CTG monitoring, and none which has compared it with IA.
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 IA. (If you have, I’d love to hear about it in the comments!) This lack of education contributes to an unease about IA as an appropriate and justifiable option for fetal 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 (though I disagree with their assumption that IA is only appropriate for women considered to be at low risk). The specifics are set out in their paper, 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?
A few years ago, I sat in my garden with two 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 that not only do they listen for changes in the rate and pattern of the fetal heart, but that there are subtle changes in the sound of the heart – sounds that can only be appreciated with a well-trained ear listening directly to the fetus. It made me profoundly sad to contemplate that the 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 this knowledge is essentially lost to us.
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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