How to Measure a Baby's Heartbeat on Doppler

When you’re pregnant, almost nothing is more beautiful to the ear than the sound of your baby’s heartbeat. This sound reassures you that your baby is still thriving. One of the most common methods to hear this sound is through a fetal Doppler. Once you know how to measure a baby’s heartbeat on Doppler, you can better understand when you can and should look to hear this beating reassurance.

Function

Fetal Doppler machines have a small wand that is pressed onto your stomach. The wand emits a form of ultrasound waves to convert the sound waves that are in your uterus into an audible heartbeat. Most ultrasound machines in your doctor’s office have a Doppler function; on these machines, the Doppler can also produce a visual representation of the blood cells as they move through your baby’s blood vessels.

To measure the baby’s heartbeat, you simply count the number of these beats over a minute’s time; you can also count the number in 15 seconds and multiply that by 4. Typically, a baby’s heartbeat is in the range of 120 to 160 beats per minute; if you get lower than that, you may be hearing your heartbeat across the placenta and not the baby’s.

Types

Currently, you will find two main versions of fetal heart Doppler machines. Many Doppler machines are built to be used in doctor’s offices, either as part of a full-service ultrasound machine or as a standalone handheld Doppler for heartbeat checks only. It’s also possible to buy or rent Doppler units that are approved for personal in-home use. You can use these in your home to hear and measure your baby’s heartbeat whenever the mood strikes.

Time Frame

The time period from which you can first hear your baby’s heartbeat via Doppler can vary from woman to woman. It’s possible to hear your baby’s heartbeat over Doppler as early as nine or 10 weeks along. However, according to Dr. Marjorie Greenfield, sometimes it may not be audible simply because of the baby’s position, the position of your uterus, your weight or even bad luck. Once you reach 12 weeks, you should be able to measure your baby’s heartbeat on the Doppler regularly.

Considerations

If you are having a difficult pregnancy, your doctor may use the visual Doppler component during your third trimester. This visual representation lets your doctor see how your baby’s blood is flowing in his vessels as well as across your placenta and umbilical cord. This is typically done in the third trimester when doctors are trying to decide if your baby should be delivered or remain where he is a little longer.

Warning

The Food and Drug Administration, or FDA, has stated that fetal heart Doppler units are not intended for over-the-counter use 3. An FDA physicist, Dr. Robert Phillips, says that there are no known risks for Doppler use, but the long-term effects of the heating of the tissues by the Doppler’s ultrasound waves are not yet known. The FDA maintains that Doppler units should only be used under medical prescription from your doctor.