Fetoscopes have been in use since the 19th century. Midwives and others worldwide continue to use fetoscopes for listening to fetal heart tones. The United States is one of the few countries where the Doppler has replaced the fetoscope. Though there are many types of fetoscopes available, the most commonly used in the Allen Type.
Fetoscopes are designed to listen to the heartbeat of unborn babies. Fetal heart tones can be detected as early as 18 weeks, but in most cases a fetoscope is most effective after 22 weeks. When using a fetoscope, you will note that the sound is very soft and far different than the amplified sound provided by a Doppler.
According to Penny Simkin, using a fetoscope is especially useful for determining fetal position.
“In most fetuses near term, the loudest sounds of the fetal heart are heard through the fetal back, at approximately the level of the scapula or shoulders. Locating this PMI [point of maximum intensity] of the fetal heart tones helps determine the orientation of the fetal back - either anterior or posterior. The best tool for this purpose is a fetoscope…which allows for the direct auscultation of the fetal heart…”1
During the 19th century, the Pinard Horn was designed by French obstetrician Adolphe Pinard, to listen to the heart rate of a fetus. The Pinard Horn is a cone shaped fetoscope that amplifies the sound of the fetal heart beat, and has been described as a type of ‘ear trumpet’. The monaural – meaning it only requires one ear for use - design “rapidly became the fetal stethoscope of choice because the widely faring bell prevented rocking on the mother's abdomen during auscultation.”2 The Pinard Horn is often made of wood or aluminum – the wooden style still popularly used amongst midwives, especially in developing countries where metal instruments are not always welcomed due to cultural superstitions.
The binaural fetoscope design that allows users to hear the heart beat through both ears is most commonly used today. The first binaural fetoscope was originally described in 1917 by David Hillis, and then later by his supervisor Joseph DeLee in 1922, who apparently claimed credit for its creation.3 As a result, the first binaural fetoscope eventually became known as the DeLee-Hillis Fetoscope.
Choosing between the monaural design of a Pinard Horn and binaural fetoscope designs really comes down to personal preference. Here is a synopsis of the different types of fetoscopes along with their corresponding features.
‘Ear Trumpets’ – PINARD HORNS
Although it is less commonly used than the modern binaural fetoscope designs, the Pinard Horn is still commonly used by midwives in a variety of countries. It is offered in both wooden and aluminum designs - the wooden option being most popular as it absorbs sound rather than reflecting sound like aluminum.
Not everyone is comfortable using the Pinard Horn because it requires a high level of spatial intimacy between the mother and practitioner. More modern binaural designs have a long tube between the earpieces and the horn to allow for more personal space if/when it is desired.
‘Get Your Head in the Game’ – DELEE-HILLIS FETOSCOPE
As mentioned earlier in this article, the DeLee-Hillis is one of the earliest fetal stethoscope designs. What makes this style unique is the headband that offers a hands-free option to practitioners. The fetoscope horn is strapped to the headband and much like the Pinard Horn, it allows you to slowly and consistently apply pressure to the belly for greater amplification of the FHR by using your head.
‘Home is Where the Heart Beat Is’ – ALLEN TYPE FETOSCOPES
Designed after the exceptionally popular - but unfortunately discontinued – Allen Series 10 Fetoscope, the Allen Type Fetoscope is our best selling fetoscope. It could be that it’s so affordable or it could be that it’s the only fetoscope available in purple – the official color of midwifery. Or it simply could be both!
The Allen Type Fetoscope has a longer 22” tube that allows mothers to listen to their own bellies. The tubing can also easily be trimmed for practitioners who want a shorter tube for better audio clarity. This design feature makes it ideal for anyone to use, whether for professional or personal use.
Unlike the DeLee-Hillis and Pinard Horn Fetoscopes, the Allen Type Fetoscope has a horn at the end of the 22” tubing that allows you to apply pressure with your hand or forehead. The design allows for more flexibility for positioning the fetoscope and is perfect for mothers who are looking for an inexpensive fetoscope that is long enough for them to hear the fetal heart beat at home on their own.
‘Big Bells’ - LEFF FETOSCOPE
Pricier than most, but definitely worth the investment, the Leff Fetoscope goes above and beyond the capabilities of other fetoscopes. The Leff features an unusual conductor that blocks external noise to isolate heart tones as well as cord and placental pulses. It has a very large, heavier bell that allows for superb sound quality, rivaling that afforded by medical Dopplers.
The Leff Fetoscope works best after 17 weeks and can effectively be used throughout pregnancy, labor, through contractions and even under water. The weight of the bell takes some getting used to and is best to warm up first in your hands before applying to a mother’s belly – simply for comfort.
As you can tell, each fetoscope offers a unique selection of features. When it comes time to choose one, there are a few things you can consider before making a decision. What will its main purpose be for - will it be used infrequently as a backup instrument, or regularly throughout pregnancy and labor? What works best for your client base - are they comfortable with close proximity examinations? Are there any cultural barriers that might make them uncomfortable with a specific style of instrument? And lastly, what are you comfortable with – do you need the option to choose from smaller or larger ear tips? Do you want to offer families a chance to use the fetoscope as a bonding instrument that anyone can use to hear the fetal heart beat?
If you enjoyed this post, the topics covered in the following blog posts may also be of interest to you: 'How to Choose the Right Doppler', and 'Why Do We Use Plastic Cord Clamps?', 'The Importance of Newborn Pulse Oximeters'. Click the post title to view the full article, or scroll through our complete archive of posts by clicking here.
Written By: Samantha Darling for Cascade HealthCare Products
1Penny Simkin, The Labor Progress Handbook: Early Interventions to Prevent and Treat Dystocia: http://www.1cascade.com/p/53167/labor-progress-handbook-3rd-edition-penny-simkin-ruth-ancheta
2The Monaural Stethoscope: http://www.antiquemed.com/monaural_stethoscope.htm
3Fetal Stethoscope History, Center for Experiential Learning: http://utilis.net/fhm/2465.htm