External fetal monitoring is an indirect, noninvasive procedure. It uses two devices strapped to the mother's abdomen to evaluate fetal well-being during labor.
The ultrasound transducer transmits high-frequency sound waves to the fetal heart. The tocotransducer, in turn, responds to the pressure exerted by uterine contractions and simultaneously records their duration and frequency. (See Applying external fetal monitoring devices.) The monitoring apparatus traces FHR and uterine contraction data onto the same printout paper.
External fetal monitoring may be used for high-risk pregnancy, oxytocin-induced labor, and antepartal nonstress—delete contraction stress tests, as they are not performed.
Electronic fetal monitor 
operator's manual ultrasound transducer tocotransducer conduction gel transducer straps damp cloth printout paper. Monitoring devices, such as phonotransducers and abdominal electrocardiogram (ECG) transducers, are commercially available.
After reviewing the operator's manual, prepare the machine for use.
Who and when
Label the printout paper with the patient's identification number or birth date and her name, the date, maternal vital signs and position, the paper speed, and the number of the strip paper.
- Identify the patient using two patient identifiers per the facility policy.
- Explain the procedure to the patient.
- Make sure the patient has signed a consent form if required.
- Perform hand hygiene and provide privacy.
Beginning the procedure
- Assist the patient to the semi-Fowler's or left-lateral position with her abdomen exposed and palpate the abdomen to locate the fundus—the area of greatest muscle density in the uterus. Then, using transducer straps, secure the tocotransducer over the fundus.
- Adjust the pen set tracer controls so that the baseline values read between 5 and 15 mm Hg on the monitor strip or as indicated by the model.
- Apply conduction gel to the ultrasound transducer crystals and use Leopold's maneuvers to palpate the fetal back, through which fetal heart tones resound most audibly.
- Start the monitor and apply the ultrasound transducer directly over the site having the strongest heart tones.
- Activate the control that begins the printout.
Monitoring the patient
- Observe the tracings to identify the frequency and duration of uterine contractions but palpate the uterus to determine intensity of contractions. Using the external monitor does not allow measurement of the strength of the contractions. Palpation of the contraction as mild can be compared to the tip of one's nose, moderate strength to one's chin, and strong to the feeling of one's forehead. This provides the nurse with a reference point as the nurse compares the assessment of strength with another experienced nurse.
- Note the baseline FHR and assess periodic accelerations or decelerations from the baseline. Compare the FHR patterns with those of the uterine contractions.
- Move the tocotransducer and the ultrasound transducer to accommodate changes in maternal or fetal position. Readjust both transducers every hour and assess the patient's skin for reddened areas caused by the strap pressure.
- Clean the ultrasound transducer periodically with a damp cloth to remove dried conduction gel and apply fresh gel as necessary. After using the ultrasound transducer, place the cover over it.
- If the patient reports discomfort in the position that provides the clearest signal, try to obtain a satisfactory 5- or 10-minute tracing with the patient in this position before assisting her to a more comfortable position. (See Documenting external fetal monitoring.)
Outline