Hearing the steady, rhythmic, whooshing sound of a fetal heart beat via a doppler device can be a comforting experience for an expectant mother. Monitoring the fetal heart rate regularly also provides a health care professional information on the general health of the fetus and the developing circulatory system.

Function

A baby doppler, or fetal doppler heartbeat monitor, is a small, handheld device that is used by health care professionals to determine the heart rate of a baby while he or she is still in the womb.

Time Frame

A fetal heart beat may be heard via doppler as early as 10 weeks, if it is placed at precisely the right angle on the mothers' abdomen. By 12 weeks, a fetal heart beat may be heard consistently, according to Dr. Marjorie Greenfield in her article on DrSpock.com.

How it Works

A transducer covered with ultrasound gel is glided over the abdomen of the expectant mother, sending pulses of sound waves that are reflected off of the fetal heart. The sounds are processed and amplified by the doppler into an audible heart rate.

Identification

If the doppler does not provide a digital read out of the heart rate, a health care professional will either count the number of beats heard for one minute or will count the number of beats for 15 seconds and then multiply the number by 4 to determine the fetal heart rate. Normal fetal heart rates range between 120 to 160 beats per minute, according to Greenfield.

Misconceptions

Some people believe if the heart rate is 140 beats per minute or higher then the fetus is a girl, while if it is lower than 140, the fetus is a boy. This was shown to be untrue, according to a 2006 study on gender-related differences in fetal heart rate that was conducted at Wright State University in Dayton, Ohio.

Source:

Dr. Spock: Hearing the Fetal Heartbeat

U.S. National Library of Medicine: Gender-related differences in fetal heart rate during first trimester