From the Guidelines
Ultrasound is recommended as an adjunctive tool to find the fetal heart rate in labor when external Doppler or electronic fetal monitoring fails to detect the fetal heart rate or when there is uncertainty about fetal viability, as supported by the most recent evidence from 2016 1.
Key Considerations
- The use of ultrasound in this context is particularly valuable in situations involving maternal obesity, polyhydramnios, fetal malposition, or early gestational age.
- A portable ultrasound machine with a curvilinear transducer (2-5 MHz) should be used, applying ultrasound gel to the maternal abdomen and scanning until cardiac activity is visualized.
- The M-mode can be utilized to document the fetal heart rate by measuring the distance between cardiac contractions.
Benefits of Ultrasound
- Provides direct visualization of cardiac activity rather than relying on reflected sound waves.
- Offers confirmation of fetal life when conventional monitoring methods are inadequate.
Documentation
- Healthcare providers should document both the use of ultrasound and the findings in the medical record, noting the fetal heart rate and any other relevant observations.
Evidence Base
- The recommendation is based on the most recent and highest quality studies available, including those published in the Journal of the American College of Radiology in 2016 1.
- These studies highlight the importance of ultrasound-based assessments in evaluating fetal well-being, particularly in high-risk pregnancies.
From the Research
Adjunctive Use of Ultrasound to Find Fetal Heart Rate in Labor
The adjunctive use of ultrasound to find the fetal heart rate in labor is recommended in certain situations.
- The use of Doppler ultrasound for continuous fetal heart rate monitoring and intermittent measurements is a common practice in clinical settings 2.
- Intermittent auscultation of fetal heart rate using a Doppler device is considered an acceptable method in low-risk labors, even in developed countries 3.
- The American College of Nurse-Midwives recommends the use of intermittent auscultation for intrapartum fetal heart rate surveillance, with equivalent long-term neonatal outcomes compared to electronic fetal monitoring 4.
Recommendations for Adjunctive Use of Ultrasound
- The Doppler device should not be used to count fetal heart tones, but rather to observe the digital read-out of the fetal heart rate and its trend during auscultation 3.
- Intermittent auscultation should focus on two fetal heart rate parameters: baseline and late decelerations, with detection of additional changes not adding value 3.
- The use of abdominal ECG and Doppler ultrasound for fetal heart rate detection has been compared, with results showing an average percent rms difference of 5.32% between the two methods 5.
Clinical Practice and Guidelines
- Electronic fetal monitoring using cardiotocography is a common tool used during labor and delivery for assessment of fetal well-being, but data suggesting improved clinical outcomes are sparse 6.
- The history of electronic fetal monitoring has been revisited, from its inception in the 1960s to current practice, interpretations, and future research goals 6.
- Clinical bulletins, such as those from the American College of Nurse-Midwives, provide recommendations for intermittent auscultation technique, interpretation, and documentation 4.