From MIDWIFERY MATTERS, Issue No.118
by Sarah Montagu
ARM has used the Pinard stethoscope as its emblem since the very first issue of its journal (ARM 1978). I wasn´t involved in ARM then but my understanding is that the Pinard, in its simplicity and its low-tech nature, was used for this purpose because it epitomises the midwifery skills which ARM espouses and encourages. But is it time, as a recent article in the British Journal of Midwifery suggests (Blake, 2008) to take the Pinard out of our midwifery bags and consign it to a glass box in a museum? Has this prime example of state-of-the-art Victorian technology finally outlived its usefulness?
The Pinard stethoscope is a refinement of the acoustic stethoscope invented by Laennec in 1816. The purpose of any stethoscope is to transmit the sounds of body processes, such as the heartbeat, to the auscultator; but it also serves the function of allowing the auscultator to get further and further from the body of the patient – originally all auscultation would have been done by pressing the ear to the relevant part of the body. Close contact of this kind is not necessarily consonant with the dignity of the medical practitioner who might not want to put his ear directly to the skin of the patient, particularly when the doctor is male and the patient female (nor with the comfort of the patient, who might not want the doctor´s whiskery ear applied to his or her chest or abdomen). The binaural style of stethoscope was therefore invented to allow the practitioner to get further and further away from the body of the patient, but the Pinard style of stethoscope was retained for obstetric use because it allows better transmission of the sounds of the fetal heart than does a binaural stethoscope. I was discussing this issue a while ago with a client who is also a midwife and a friend – I had used the opportunity of an antenatal visit to compare different types of Pinard and different materials used to make them – and in the course of the conversation, said that I had never actually tried listening directly to the fetal heart. ‘Have a go!´, she said and I was astonished by how much louder and clearer the fetal heart was when I put my ear straight on her abdomen.
However, I´m not of course advocating that we go back to asking all our clients if we can dispense with stethoscopes of all kinds and only use our ears (though I do always recommend it to partners as a way of demystifying the whole process of auscultation of the fetal heart, as if we as health professionals are seen to use Pinards and ultrasound devices, it makes it seem as if these are intrinsic to the process rather than artificial aids). So why should we still use a simple piece of wood or plastic, when we can use a technologically advanced machine that renders the heart audible to everyone in the room?
There are numerous advantages to the Pinard, few of which Blake appears to have considered. The most obvious is that one is listening directly to the sounds created by the flow of blood through the heart as the heart valves open and close, rather than hearing an artefact created by the emission of ultrasound energy from the probe and the use of the Doppler effect to measure the differences in the echo of that ultrasound energy created by the velocity of blood flow in the beating heart (or in blood vessels or in the placenta or even in the amniotic fluid). As any midwife knows who has used both a Pinard and a Doppler, one can ‘hear´ the heartbeat over a much wider area of the abdomen with the latter, so that the Pinard can be an extremely useful tool in confirming one´s palpation. This is particularly the case with posterior presentations, when a Doppler may pick up a clear beat in the usual position one would expect with an anterior presentation, whereas the heartbeat sounds more indistinct with a Pinard until one moves right round to the woman´s flank. It can also be useful in contributing to the detection of a breech presentation, although with the caveat that in a well-engaged breech, the heartbeat can still be heard relatively low on the abdomen.
Listening directly to the baby´s heartbeat might also enable the earlier detection of fetal problems than listening indirectly via an electronic artefact (Cronk 2002). Although NICE no longer recommends routine auscultation in the antenatal period, I feel it can be particularly useful where there is continuity of care, as one can build up a picture of what is normal for that individual baby and may hence be able to pick up on signs of trouble earlier than if one had never listened in prior to labour. However, it is worth reminding ourselves that there is no predictive value in hearing a heartbeat antenatally and that if we do it, we are doing it to build up a passing acquaintance with the baby whose mother is in touch with and aware of 24/7. The current fashion for selling Dopplers to pregnant women implies that artificial monitoring is in some way protective; instead it disempowers women and casts implicit doubt on their ability to be conscious of their own baby´s well-being through their constant awareness of the baby´s movements and activity patterns.
The quality of the sound heard through the Pinard should enable one to detect the difference when listening directly over the baby´s heart or when listening to the sound of the vessels of the placenta. It is particularly useful when the mother´s heart-rate and the baby´s are not that different, which can occur even in healthy women, and also in those sad circumstances where there is no fetal heartbeat to detect. We are all aware of cases where yards and yards of ‘fetal´ monitoring have been carried out in labours after which macerated babies have eventually been born.
The Pinard´s green credentials are obvious: it requires no batteries and no maintenance and can be made from a natural, carbon neutral and biodegradable material if one uses a wooden rather than a plastic Pinard. It is cheap so can be used by maternity services anywhere, in the developing as well as in the industrialised world. It does not demand the use of ultrasound energy, which many see as worth avoiding until it is shown to be safe (as opposed to not being shown to be unsafe). Although Blake claims that the ‘risk of ultrasound waves is “…negligible when using the hand-held Doppler’ (Blake, 2008), she bases this claim on a study looking at diagnostic ultrasound scans (Goldberg & Verny 2007). The frequencies used by fetal monitoring units, however, are very different from those used by fetal imaging units. Dopplers generally use lower ultrasound frequencies (typically 2 mHz) because they allow greater penetration into body tissues. They are also nearer to the boundaries of human hearing (20 Hz – 20 kHz), and it is possible that unborn babies are aware of the ultrasound ‘noise´ produced by the probe when auscultation is undertaken. Moreover, there will always be some clients who prefer their attendants not to use Dopplers for auscultations and it is therefore vital that midwives retain their skills in using the Pinard for these clients.
The Pinard is indeed less flexible for use during labour, as it takes a certain amount of practice to listen with it when the woman is in different positions and it can be completely impossible if the woman is on all fours. In this scenario, the fetascope comes into its own. This is more widely used in the United States than here, but offers two main advantages. It is a small Pinard-style stethoscope with a narrow bell but rather than the sound being transmitted along its length, the bore leads to a small stub to which binaural stethoscope tubing is attached. This means that instead of needing a clearance of about 40 cm (16’) between the woman´s abdomen and the floor to allow space for the Pinard and the midwife´s head, one only needs a maximum of 20 cm (8’) to allow for the body of the fetascope and the midwife´s hand. It also allows anyone to listen to the fetal heartbeat through the binaural tubing, including obviously the woman herself. My fetascope was worth its purchase price for this alone, as it is wonderful to see the expression on the woman´s face as she hears her baby´s heart beating for the first time.
The other hotly debated issue is whether it is possible to hear variability through a Pinard. It is my contention that it is. Human beings have an innate sense of rhythm, which therefore enables us to detect variations from a steady rhythm, which one can be subjectively aware of while listening over a minute. One of the principle uses of a Doppler or the sound of a CTG can be to train your ear. If you are listening to a heartbeat via one of these, get into the habit of assessing the rate and variability just by listening, without looking at the print-out or the digital display, and then check to see whether you´re getting it right. Any midwife can hear the ominous sound of a deceleration through a CTG machine without needing to look at the numbers on the bit of paper; it is not significantly harder to tune your ear in to hearing rates and variability which is a skill you can then transfer to the use of a Pinard. One can also do it objectively by listening to the fetal heartbeat with the Pinard, while concentrating on the second hand of your watch, and continually counting the number of beats heard in 5 seconds over a minute.
| Beats per minute | Beats per 5 seconds |
| 192 | 16 |
| 180 | 15 |
| 168 | 14 |
| 156 | 13 |
| 144 | 12 |
| 132 | 11 |
| 120 | 10 |
| 108 | 9 |
| 96 | 8 |
| 84 | 7 |
The lowest figure you get in 5 seconds will be the baseline and the higher figures will show the degree of the variability. As you are close to the woman´s abdomen, you may well be aware of fetal movements (or you can get the woman to tell you) or of contractions, which will enable you to hear if there are accelerations or decelerations.
The Pinard is not just a relic of a by-gone age or a piece of redundant technology, it is a living and useful tool which can be used to complement the skills of our hands, ears and eyes. The hand-held Doppler is useful too but cannot replace the Pinard as it cannot do everything that the latter can and lacks its elegant simplicity.
Blake D (2008). ‘Pinards: out of use and out of date?´ British Journal of Midwifery, 16, 6, 364-365.
Cronk M (2002). ‘Me and My Pinard´s´, Midwifery Matters, 94, 3-4.
Goldberg H & Verny T (2007). ‘The potential risk of ultrasound examinations on fetal development´, Journal of Prenatal and Perinatal Psychology and Health, 21, 3 261-269.
This article was originally published in Midwifery Matters issue 118, Autumn 2008 , p3
AH updated 21 October 2009