What handheld Doppler device is used to listen to a fetus's heartbeat?

A handheld Doppler device used to listen to a fetus’s heartbeat is a Doppler fetal monitor.

The monitor uses a small ultrasound transducer placed against the pregnant patient’s abdomen. Moving heart structures reflect the ultrasound at shifted frequencies, and the device converts those changes into an audible heartbeat-like signal. Some models also calculate and display fetal heart rate in beats per minute.

The device is often shortened to “fetal Doppler” or “Doppler,” and “Sonicaid” is a commonly encountered genericized name in some regions. It differs from an otoscope, which examines the ear; a spirometer, which measures lung function; and a pulse oximeter, which estimates blood oxygen saturation.

Dr. Edward H. Hon is credited with inventing the device in 1958. Although handheld Dopplers can make fetal cardiac activity audible, hearing a signal does not by itself establish fetal well-being, which is why clinical interpretation belongs to trained healthcare professionals.