Instruments Used to Hear a Heartbeat

A heartbeat, when it's pumping at the proper rate, is easy for a doctor to recognize. And when that heartbeat is irregular, it can tell medical professionals a lot about what might be wrong. This is true even of unborn babies, whose heartbeats are regularly monitored by both doctors and expectant parents.

Stethoscope

• The purpose of a stethoscope is to listen to sounds made inside the human body. While a stethoscope can be used to listen to the stomach or the lungs, it's also used to listen to the heartbeat. These instruments have two ear buds connected to a sensitive sound detector that hangs on the end of a connecting cable. The stethoscope is traditionally associated with doctors, and in dramatic productions, the actor playing a doctor often has a stethoscope slung around her neck.

Doppler Instrument

• A common instrument for listening to the prenatal heart is called the Doppler instrument. This piece of medical equipment sends sound waves into a pregnant woman's womb. These waves act in a similar manner to sonar waves, and are affected by the sound and force of the fetus's beating heart. When the fetal heart beats, it changes the reflection of the sound waves and creates a distinctly different sound. Using this method, the doctor and the mother can hear the unborn baby's heartbeat, as interpreted by the Doppler instrument.

Pre-Natal Monitor

• Doppler instruments--meant to amplify an unborn baby's heartbeat from the time the fetus is still very small--are large and expensive. Less expensive versions of this technology are sold for home use, and these devices are simply called pre-natal monitors. The sound waves pre-natal monitors create are less precise and powerful than a those created by a Doppler instrument, so these small instruments are used later in pregnancy (roughly 10 weeks and up) for women who want to be able to monitor their unborn baby's heartbeat.