A Doppler fetal monitor is used to detect the heartbeat of a fetus.
The device is a handheld ultrasound transducer used during prenatal care. It sends high-frequency sound waves into the body and analyzes changes in the returning waves caused by moving heart tissue and blood. The monitor converts those changes into an audible simulation of the fetal heartbeat, and many models also display a heart rate in beats per minute.
The technology is commonly called a fetal Doppler, Doppler, or Sonicaid, although Sonicaid began as a trademarked name. It is related to Doppler ultrasonography, but a simple monitor primarily produces sound rather than creating a diagnostic image.
A fetal Doppler is not the same as a fetal stethoscope. A stethoscope relies on acoustic sound transmitted through the body, while the electronic Doppler can amplify the signal so other people can hear it too. Hearing a heartbeat is reassuring, but professional prenatal assessment involves more than the monitor alone.