Fetal Doppler

Everything there is to know about fetal doppler

The fetal doppler is a portable, easy to handle, ultrasound transducer commonly used in healthcare settings to detect the fetal heartbeat. Similar to the fetal stethoscope, it gives the necessary details about the baby's heartbeat. It is also known as doppler auscultation or simply doppler and is grouped as a type of doppler ultrasonography, using the Doppler Effect to give a perceptible facsimile of the human heartbeat. Only a few models show the pulse in beats per minute (BPM). Typically, medical practitioners use doppler with a frequency of 2-MHz or 3-MHz. A probe with 3-MHz can easily sense heart rate in the earliest days of pregnancy (8th -10th week) and is commonly used with obese pregnant women. A new 5-MHz probe that works transvaginally has outperformed the 2-3MHz probe by detecting a heartbeat as early as during the 6th-8th gestational week. It is also ideal for obese females or pregnant women with a retroverted uterus.

Presently, a range of dopplers with different specs and models are available in the market. Dopplers are available both for hospital use as well as for home use. For home usage, they differ significantly in their functioning and handling. Viewing increased use of their home versions, FDA formally issued a report not recommending their usage because of many threats they pose to the baby's health and life. The general public may misuse it outside the optimal frequency range, which can result in thermal or non-thermal effects, overdue mechanical stress, and radiation force.

History of fetal dopplers

Although the use of ultrasound is widespread in today's life, it was not the same for a long time. It is not exactly ancient and did not get commonplace until the 1960s. The very first recorded utilization of ultrasound for clinical reasons was in 1956. An obstetrician, Ian Donald, and an engineer, Tom Brown, were the first persons to use it in history. These two men built up the main framework for ultrasound, yet it was not utterly perfect until the 1960s. After its first usage in obstetrics, it experienced various changes. The first change was made in 1966 when Dennis Watkins, John Reid, and Don Baker made the heartbeat doppler ultrasound technology. This innovation took into account the imaging of blood flow through numerous layers of the heart. In this way, Don Baker became a focal figure in the development and creation of the primary medical used doppler instruments for the non-invasive investigation of blood flow and movement of body organs. The creation of primary 3D ultrasound innovation was in the 1980s, and the first primary 3D picture of the human fetus was taken in 1986. During the 1980s, ultrasound began to turn out to be progressively modern in terms of technology. During the 1990s, the selection of 4D abilities got conceivable, and ultrasound-guided biopsies started to surface.

Today, ultrasound keeps on developing innovations. Handheld gadgets are relatively common. It has utilization in every medical field to investigate the blood vessel and organ movements. Before its invention, we used invasive angiography. Presently, we can non-intrusively and securely study the blood circulation of humans, including unborn baby circulation, and we are privileged to have this critical innovation with us.

Indications to use fetal doppler

Fetal doppler has been an essential obstetric instrument for more than 30 years. It may be utilized to evaluate both the unborn baby and placental blood flow circulation, with the point of assisting the diagnosis and observation of significant conditions like fetal growth restriction (FGR), anemia, and twin-to-twin transfusion syndrome (TTTS). 

Here we are going to list all the essential indications which require the use of dopplers:

  • Fetal growth restriction: In the case of growth restriction, we use doppler for the observation and timing of delivery compromised because of growth restriction. It surveys impedance inside the baby and placental blood flow. It is both a prognostic and diagnostic device in the evaluation of a baby's growth restriction. The waveform exhibiting growth development becomes apparent after 12 days of the baby's deterioration.
  • Anemia: Commonly utilized to evaluate pregnancies with a higher risk of anemia, e.g., Rhesus isoimmunization. It is used to keep away superfluous invasive options in pregnancies complicated with red blood cell isoimmunization.
  • Cardiovascular deterioration: The doppler goes about as a marker of cardiovascular deterioration explicitly in the beginning stage of growth restriction. It can give a clue to academia and stillbirth, which is the leading indicator of the danger of fetal death.
  • Pre-eclampsia:  Doppler measurements can screen a problem like pre-eclampsia. The advantage of performing such an evaluation is that it helps in starting treatment about four months before the 16th gestational week to lessen the danger of pre-eclampsia by 17% in risky pregnancies. 
  • Checking imbalance between the impedance of the brain and systemic circulation: If recording shows any abnormality, it can be an indicator of unfavorable perinatal outcomes and subclinical cardiovascular abnormality. 
  • Atrioventricular valves: Also used for the assessment of the atrioventricular valves, both mitral and tricuspid valves. The diagnosis of tricuspid regurgitation has been accounted for to have prognostic significance in perinatal forecasting outcomes.
  • Aneuploidy screening: t can help to distinguish the possibility of aneuploidy or congenital cardiac defects.  
  • Twin-to-twin-transfusion syndrome (TTTS): Commonly utilized in monochorionic twin pregnancies affected by TTTS in which its measurement status is a significant prognostic marker for TTTS. Consequently, it can help direct practitioners in the treatment of patients. The concurrence of TTTS with tricuspid regurgitation is an indicator of severe TTTS. 
  • For enhanced fetal surveillance: Might be used to show decreased, missing, or reversed umbilical artery end-diastolic flow, which is a sign for enhanced surveillance.
  • Intrauterine infection: It can be useful in predicting a situation where there is a risk of infection of amniotic fluid that can cause impaired fetal perfusion.

Complications of using the fetal doppler

The fetal doppler users commonly see it as a protected method with no harmful impacts. Since ultrasound is utilized in pregnancy, all medical professionals need to keep their utilization in a safe zone. Thus, medical professionals must know the complications that can arise from its usage. The two main problems caused by the effects of ultrasound can be cavitation and heat energy.

Thermal effects: After reaching into the body, the ultrasound waves readily convert into heat energy. The degree of heat conversion and assimilation is most noteworthy in body tissues with a high absorption coefficient, especially in bones, and is low in tissues with a low absorption coefficient, e.g., amniotic liquid. The essential worry in this imaging is the temperature rise because it can have teratogenic effects on the unborn baby's body. Moreover, temperature rise for an increased time also causes harmful biological effects. The transducer face itself can get heated during an assessment time and poses a burning threat to the skin, but it is rare.

Cavitation: It is the development of air bubbles that could be transient or stable inside the tissues. Some of them can affect the baby's tissues. Breakdown of the air bubbles can create high temperatures and pressure locally, speculated as being the main reason for lung hemorrhage and intestines of the human body.

Alternatives to fetal dopplers

An alternative to using a fetal doppler is non-invasive abdominal electrocardiograms (ECG). This alternative, regarded as a potential improvement in technology, offers concurrent baby and maternal heartbeat detection. This innovation also helps to distinguish the confusion while detecting heartbeats. The permission for non-invasive abdominal electrocardiograms for clinical usage was given in 2008. It is particularly useful during the initial stage of labor as it exhibits better quality when contrasted with signals utilizing the fetal doppler with which finding signals are difficult. Moreover, ECG signal working is not affected by BMI. 

On the other hand, for the vernix period, doppler is highly recommended. Also, its signal working is affected by BMI. Beyond this time, no distinction exists in the functioning of either approach.

General specifications of fetal dopplers

There are several designs available on the market, with different specifications; however, we are going to cite the general specifications, which are accurate enough.

The specifications provided by WHO:

Approx. dimensions (mm): 100 x 150 x 200

Approx. weight (kg): 1

Consumables: Batteries, gel

Price range (USD): 350 - 800

Typical product lifetime (years): 8

Other specifications include:

  • Handy to use
  • Working on Rechargeable battery
  • Having an ON/OFF button
  • Have an LCD for heart rate.
  • Auto counting
  • Must have a probe storage facility to avoid accidental falling
  • Have a facility for controlling the volume of heart rate sound
  • Provided with a rechargeable battery.
  • Having an automatic power-off facility.

How the fetal doppler works

Its working is simple. When the practitioner simply directs a handheld probe to maternal womb, ultrasound waves having frequency 2-3 MHz or 5 Hz in the case of transvaginal, are transmitted into the maternal uterus and absorbed by blood vessels. The waves return after knocking with blood in the vessels, and this hitting changes their original frequency. The ultrasound machine estimates the change in frequency, and the practitioner can determine the blood speed or the baby's heartbeat. It detects any blockage in blood flow or any blood clot, which results in impedance to normal blood flow to the baby's body. A positive perspective is that it can bring up any coming illnesses about half a month before different symptoms show up so that the practitioner can start life-saving treatment.

Market Leaders

Parents desire to listen to their new little angel's heartbeat with a fetal doppler, but we strongly suggest you not to use them at home. A statement issued by FDA says that using home version fetal dopplers can be dangerous to your unborn baby. It is better to consult your practitioner and work on his guidelines.

Here, we mention some leading brands with their outstanding and innovative products.

Huntleigh has been manufacturing dopplers for over 40 years and has been introducing innovations to it. They have one of the best-selling products worldwide. Their products provide outstanding probe performance, exceptional digital audio, high-resolution color displays, sound recording, and rechargeable batteries.

Sonoline provides fetal dopplers that are very handy, and anyone can master their usage. The company also provides the money-back guarantee and ensures that you will be happy working with their product. 

Newman Medical has been manufacturing dopplers for over 40 years. They offer long-lasting and sensitive products that produce clear, sharp fetal sounds.



Fetal dopplers play an essential part in detecting fetal blood circulation and predicting any abnormality or condition which can affect the baby and treatments to protect the baby. They are widely available in the market at reasonable costs. It is also very crucial for medical professionals to thoroughly understand its working so that they never miss any critical findings.

Deltex Medical Esophageal Doppler Probe 9070-7006   Item Past Expiration 032329/2
 Philips L12-5 broadband linear ultrasound transducer is compatible with Philips iU22, HD11 XE, HD15, HD7, HD9 and EnVisor ultrasound systems. The L12-5 probe can be utilized for vascular, small parts, breast, and musculoskeletal imaging applications. It features 10 degrees of trapezoidal imaging, XRES, as well as color Doppler.