Doppler Use in the Pregnancy Center

By Kimela Hardy, MA, RT(R), RDMS

Ultrasound is highly developed technology, a modality that remains a prescription device, and affords an easy opportunity to “Take A Peek” at an unborn/preborn child, and in pregnancy centers demonstrating life to an abortion - vulnerable woman.

The efficacy of using ultrasound in crisis pregnancy centers is undeniable with a reported nearly 90% of abortion minded women choosing life for their child after seeing their unborn/preborn child with ultrasound. According to Right to Life latest available information January 2012, at least 23 states have laws pending which require an ultrasound be done prior to an abortion.

As a result some abortion centers now offer ultrasound scans for an additional fee unless otherwise dictated by law. However due to the generosity of organizations and individuals many crisis pregnancy centers can now offer free ultrasounds to their clients in order to demonstrate life. In general, registered nurses are trained to perform a very limited 2D (Dimensional) or B – Mode (Brightness Mode) obstetrical scan to determine fetal viability and gestational age.

While the use of ultrasound is medically accepted as having “no known biological effects”, the effects of Doppler use remain undocumented and relatively unknown. The premise is women who hear the audible sound may decide against having an abortion and continue the pregnancy to term.

However, another and much preferred method to demonstrate the fetal heartbeat while demonstrating life to an abortion vulnerable woman remains easily available by utilizing “M-Mode”, or Motion Mode. This clearly shows the beating heart without the potentially adverse side effects of Doppler (which has 7-9 times the energy) on a very small and forming fetal heart. If someone wants to hear a fetal heart beat, the response is “we can do better than that, we can SEE the heart beating!”

So what, if any, difference is there to the unborn baby and mother if Doppler is used in addition to 2D ultrasound? Additionally, what does using Doppler do to our client, both mother and unborn child?

Doppler uses high(er)-intensity sound waves to evaluate blood flow/movement. Adults undergo Doppler medical tests for cardiac irregularities, carotid occlusions, and venous and arterial interrogations where the benefit of medical information outweighs any potential risks. Medical indications for Doppler performed in 3rd trimester of pregnancy are for high risk patients, mothers with high blood pressure, diabetes, renal problems, or any other conditions which may affect the fetal growth to diagnose potential complications affecting fetal outcome. The Doppler is focused on the umbilical cord between the uterus and placenta, and not on the forming heart. In fact, specifically mentioned is the unlikelihood of any fetal safety implication as long as the embryo/fetus lies outside the Doppler beam, in this instance referring to Doppler use in 3rd trimester.

All resources state there are “no known biological effects” using ultrasound prenatally, in other words there are no documented reports of adverse fetal outcomes. The American Institute of Ultrasound in Medicine and the American Congress of Obstetrician and Gynecologists state ultrasound should be done in a “prudent manner”. And another AUIM release states bioeffects may result from inappropriate Doppler use or excessive thermal ore mechanical index setting.

In the pregnancy centers, Doppler is sometimes used to hear blood flow through the heart, and this is usually done in very early first trimester. However, an AIUM Statement approved April 18th, 2011, states the use of Doppler in the first trimester should be viewed with great caution and only when any benefit outweighs any potential risk. Further, it recommended Doppler should not be performed routinely.

Doppler uses considerably more energy, which is directed at the fetal heart during attempts to obtain fetal heart sounds the first trimester. Intensity is the quantitative factor to determine instrumentation output, and while exposure is somewhat difficult to quantify, scan length and other technical factors are important to consider. Also, variation in tissue properties influence dose in an unpredictable manner.

Please refer to the table below which clearly demonstrates a substantial increase in power when using Doppler:


Doppler: Mode of U/S Used

Average Value Intensity Range
(Spatial Peak, Temporal Average)

B-Mode 0.1 to 60 mW/sq cm
Doppler Mode 1.0 to 200 mW/sq cm
Hand held Doppler Systems 0.2 to 20 mW/sq cm2

ALARA Principle

A basic principal practiced in ultrasound is As Low As Reasonably Achievable, ALARA, using the lowest possible energy while producing a diagnostic image. As the above chart demonstrates, using Doppler increases the power significantly a contradiction to ALARA.

Another factor affected by ALARA is transducer/probe movement. Keeping the transducer/probe in one position without movement will increased tissue temperature (Thermal Index) and cavitation will occur in the structures within the beam’s focus. Thus, the transducer/probe should not be held in a fixed or stationary position any longer than necessary to obtain a diagnostic image. The transducer/probe should be either lifted off the patient and/or the image frozen when there is no need for additional image acquisition. (Cine loop can be accessed for continual observation.) Doppler is acquired by maintaining constant placement of the transducer/probe, in this case on the very small embryonic or fetal heart, further increasing Temporal Intensity.

This is especially significant with endo-cavity, or in the PCs transvaginal, scanning where the surrounding tissue is approximately 37°C/98.6°F rather than room temperature as in Transabdominal scanning. When Doppler is used and the fetal heart beat is audibly being heard, the transducer is held in one location and moved around.

For more, see


As long as any possibility of injury to the fetal heart remains, performing Doppler on these forming and early heart cells is not recommended, especially in Pregnancy Centers where nurse sonographers have limited training and sonography skills. Instead, the sonographer can visually demonstrate-show- the fetal cardiac activity, “A Picture is Worth a Thousand Words”. The lack of proper training and experience to acquire a fetal heart beat on M-mode does not necessitate the use of Doppler. Instead, continual development as assessment of scanning skills utilizing depth/size, manufacture specific enhancements, etc. will produce a visual and real-time fetal heart beat to the abortion vulnerable woman.

It is in the presentation of the medical personnel to the client/patient how seeing the fetal heart beat will eliminate the need to use Doppler. Then replay this clip on a continuous cine-loop for continual observation of the fetal heart and fetal activity while completing the patient/client’s appointment. It is also important to note that OB is the most litigious medical field, and there remains a potential medical liability to Pregnancy Centers so standard practices are highly recommended, and Doppler use to hear the fetal heart beat is not a standard practice in the Medical Imaging field.

It has also been suggested by some that in dire instances where the client/patient is determined to end the pregnancy with an abortion, Doppler should be done in a “Hail Mary” attempt. If this is the recommendation/order by your medical director, armed with the above information, one must proceed with great caution recognizing that the unborn/preborn life may be saved from abortion but with the knowledge of potential risk of cardiac issues.
Outside of the Pregnancy Center and in clinical practices, Doppler is not done routinely by Registered Diagnostic Medical Sonographers, not even in 1st trimester to determine fetal cardiac activity. If a heartbeat is visualized but not able to be measured, a note will be on the report that cardiac activity was demonstrated.

It is important to note that an ultrasound scan is critically dependent on the operator and his/her education and experience. While safe, even for the developing fetus, ultrasound and especially Doppler should only be done by fully trained personnel in its safe and proper operation, and who thoroughly understand the physics involved. With all of this knowledge, in limited OB training for pregnancy center nurses, Doppler is not recommended for use on pregnant models generously volunteering their preborn child.