More recently, fetal dopplers have been sold over the counter (OTC) for at-home use.
Around that time, a fetal heartbeat may be detected with a transvaginal ultrasound.
It gets its name from how it works, using the Doppler effect.
Nensuria / Getty Images
Unlike an ultrasound scan, a fetal doppler only produces sound, not an image.
Fetal dopplers are made up of two partsthe probe and the main unitconnected by a cord.
To use the gadget, a healthcare provider will place gel on the end of the probe.
The gelled probe is then moved around a pregnant persons bare abdomen until it detects fetal sounds.
Sounds are audible through the speaker on the main unit.
Fetal heart tones typically fall between 110 and 160 beats per minute.
These dopplers are particularly useful when a person is laboring in water.
Dopplers come in a variety of strengths, measured in megahertz (MHz).
MHz is defined as one million cycles per second.
Fetal dopplers used in healthcare providers offices and sold for OTC use are usually 2 MHz or 3 MHz.
For comparison, a probe used for a transvaginal ultrasound can be as high as 5 MHz.
But the doppler isnt the only unit that can be used to hear your babys heartbeat.
Here are some others:
Is It Safe?
Fetal dopplers are medical devices that are designed for use by medical professionals.
Ultrasound can heat and produce small bubbles in tissues.
Doppler use by laypeople also can result in unnecessary alarm or false reassurance.
There are alternative devices for listening to your babys heartbeat.
In early pregnancy, a transvaginal ultrasound is used to detect a heartbeat.
Yes, when used in a professional setting, fetal dopplers are safe.
There is no evidence that fetal dopplers can cause harm to an unborn baby.
The FDA advises against home use of doppler ultrasound heartbeat monitors.
According to the FDA, these devices should only be used under the supervision of a healthcare professional.
In addition, using a fetal doppler without training can cause additional anxiety for the mother.
At times, it may be difficult to find a heartbeat, which can cause unnecessary worry and stress.
U.S. Food and Drug Administration.Avoid fetal “keepsake” images, heartbeat monitors.
Cleveland Clinic.Prenatal care & your first pregnancy appointment.
Edwards K, Itzhak P.Estimated date of delivery.
National Center for Biotechnology Information.
American College of Obstetrics and Gynecologists.Obesity and pregnancy.
2019;14(7):e0219573.
doi:10.1371/journal.pone.0219573
Michigan Medicine University of Michigan.Fetal monitoring during labor.
John Hopkins Medicine.Fetal heart monitoring.
U.S. Food and Drug Administration.Ultrasound imaging.
