Fetal Doppler is an obstetric test used to listen to a baby’s heartbeat. When used as part of an ultrasound exam, it can evaluate blood flow in the fetus and placenta, and help check the baby’s well-being.
Some pregnant people use portable fetal Doppler devices to try to hear the baby’s heartbeat at home. Even when used at home, these devices should not replace prenatal care or clinical evaluation.
Medical guidance is important to correctly interpret what is heard through the device. A fetal Doppler can pick up many normal body sounds, such as blood moving through vessels or intestinal movement, which may be mistaken for the baby’s heartbeat.
What it's used for
During a prenatal ultrasound, a fetal is used to:
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Monitor the baby’s blood circulation;
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Listen to the baby’s heartbeat;
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Check whether fetal organs are receiving an adequate blood supply;
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Evaluate blood circulation in the umbilical cord and uteroplacental circulation;
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Assess blood flow in the baby’s aortic, renal, and cerebral arteries.
A Doppler ultrasound can detect changes like placental insufficiency or fetal anemia, among other issues. According to the American College of Obstetricians and Gynecologists (ACOG), Doppler ultrasound (including Doppler examination of the umbilical artery) is one of the tests used to monitor fetal well-being in pregnancy.
The exam is conducted by an OB/GYN or maternal-fetal medicine specialist, typically in a hospital or imaging clinic.
When it's indicated
Fetal Doppler is most often indicated to investigate causes of fetal growth restriction or to help identify preeclampsia.
It may also be indicated in pregnancies complicated by gestational diabetes, high blood pressure, chronic kidney disease, too little or too much amniotic fluid, or a twin pregnancy.
Fetal Doppler can also be used to help identify the cause of decreased fetal movements.
How it's done
A fetal Doppler exam is done together with an obstetric ultrasound using a device called a transducer that is connected to an ultrasound machine.
To use the transducer, the doctor applies a thin layer of gel to the pregnant person's abdomen. This helps create color images of blood vessels and blood flow that can be viewed on a computer.
The results of a fetal Doppler ultrasound should be reviewed and interpreted by the OB/GYN or maternal-fetal medicine specialist.
Portable fetal Doppler
Portable fetal Doppler devices allow clinicians to listen to the fetal heartbeat during routine prenatal visits. Some pregnant people also use them to listen to the baby’s heartbeat at home, although this is not typically recommended.
How to use
A fetal Doppler ultrasound is best performed with the patient lying down and a full bladder, as this positioning helps optimize visualization and reduces the risk of confusing maternal blood flow sounds with the fetal heartbeat.
It is also important to use a clear, water-based gel to help transmit sound waves.
When can you hear baby’s heartbeat?
With a portable fetal Doppler, it may be possible to hear the baby’s heartbeat starting around the 12th week of pregnancy.
However, this can vary based on the device type, since some devices may detect a heartbeat as early as 9 weeks, while others may only work after 16 weeks of pregnancy.
When to use
It is recommended to ask your OB/GYN or midwife for guidance when using a portable fetal Doppler for the first time. This helps ensure the device is used correctly and that the sounds are interpreted appropriately.
This is important because normal body activity, such as intestinal movement or blood flow, can create sounds that the device detects. It is also possible not to hear the baby’s heartbeat, which can be influenced by the device type, correct use, the baby’s position, or gestational age.
According to the Association of Women’s Health, Obstetric and Neonatal Nurses (AWHONN), decreased fetal movement reports require prompt evaluation of fetal well-being, ideally within 2 hours of the pregnant person's report.