16.3: External and Internal Monitoring
By the end of this section, you will be able to:
- Explain how to perform intermittent auscultation of the fetal heart rate and manual palpation of uterine contractions, as well as state the advantages and disadvantages of intermittent auscultation
- Explain the placement, advantages and disadvantages, and indications for continuous external electronic fetal heart rate and uterine contraction monitoring
- Interpret the electronic fetal heart rate and uterine contraction monitor graph
- Document the assessment data of the electronic fetal heart rate and uterine contraction monitor graph
Monitoring the pregnant person and the fetus and analyzing the FHR and contraction patterns are essential parts of the nurse’s role during the antepartum period and the labor and birth process, allowing the health-care team to anticipate and prevent complications. The nurse educates the pregnant person regarding what type of monitoring is recommended at certain stages of pregnancy and labor. Providing a choice of monitor type when applicable encourages shared decision making during this important time for the person and the family.
Three methods of monitoring the fetal heart rate and uterine contractions can be used when the nurse is caring for the antepartum or intrapartum pregnant person. The first is intermittent auscultation; the other two methods—one performed by attaching external electronic monitors and the other by inserting internal electronic monitors—provide the health-care team with continuous feedback on the fetal heart rate and uterine contractions.
Intermittent Auscultation
The technique of assessing fetal well-being by listening to and counting the fetal heart rate for a specified amount of time and at specified intervals, depending upon the stage of labor, is called intermittent auscultation (IA) . The nurse palpates the uterus to evaluate the contractions’ duration (from the beginning to the end of the contraction), intensity, and frequency (from the beginning of one contraction to the beginning of the next contraction). The nurse listens before, during, and after the contraction to evaluate for any FHR changes. The nurse may perform IA with either a fetoscope or a Doppler monitor. The fetoscope is similar to a stethoscope but also uses bone conduction to allow for better detection of the FHR. The fetoscope can be used after 20 weeks’ gestation; prior to that time, the FHR is not detectable by fetoscope. A Doppler monitor is a handheld device that uses ultrasonic waves to detect the FHR. Dopplers are used in antepartum visits as well as during labor. When auscultating the FHR, it is important to assess the maternal heart rate at the same time to ensure the Doppler is providing fetal data.
Determining Optimal Placement of the Auscultation Device Using Leopold’s Maneuvers
Determining the position of the fetus is important when placing the ultrasound transducer or fetoscope on the abdomen of the laboring person. Leopold’s maneuvers are performed to assist in identifying the fetal position. The nurse performs the maneuvers, locates the fetal back, and then places the transducer on the laboring person’s abdomen directly over the fetal back where the fetal heart is the loudest. Figure 16.16 illustrates where to hear the FHR most clearly when the fetus is vertex or breech. Figure 16.17 illustrates Leopold’s maneuvers to determine the fetal presentation and position.
The nurse explains to the patient that these maneuvers require touching of the abdomen to discover how the fetus is lying inside the uterus. The nurse will lower the head of the bed with the patient on their back and begin the assessment.
- The first maneuver is done facing the patient. Both hands palpate the top of the abdomen to determine the shape, mobility, and size of the fetal part. A hard, round fetal part is the head and would diagnose the fetal position as noncephalic. A larger, softer fetal part is the buttock or back of the fetus.
- The second maneuver is used to determine the placement of the fetal back. After determining what is in the fundus, the hands slide down to the sides of the uterus and determine the fetal lie. If the nurse determines the fetal lie is longitudinal (or oblique), using the palms, the right hand holds the uterus while the left palpates for a smooth long back or small, “bumpy” extremities. The opposite side is then palpated. If the nurse determines the fetal lie is transverse, the nurse will palpate the fetal head on one side and lower extremities on the opposite side. The fetal back will face either the fundus or the cervix.
- The third maneuver determines the presenting part in the pelvic inlet. Holding the hand in a “C,” the thumb and fingers grasp the fetal part in the low abdomen above the pubic bone. Again, if the part is hard and round, it is the fetal head. The nurse can attempt to move the head back and forth to determine if the head is engaged in the pelvis.
- The fourth and last maneuver is used to determine the fetal descent into the pelvis. Turning to face the laboring person’s feet, both hands palpate down the sides of the uterus to the pubic bone and presenting part. The brow cannot be palpated if the fetal head is well flexed and engaged.
After performing the Leopold maneuvers and determining the placement of the fetal presentation and back, the nurse places the ultrasound transducer or Doppler to assess FHR.
Determining Appropriate Intervals for Intermittent Auscultation
Timing of IA is determined by the stage of labor, facility protocols, and health-care provider’s orders. AWHONN (2018) has published recommended intervals for IA based on stages of labor. Table 16.3 summarizes these guidelines for IA. The FHR is auscultated before, during, and after a contraction.
| Latent Phase Labor (4–5 cm) | Active Phase Labor (≥6 cm) | Second Stage Labor Passive Descent | Second Stage Active Pushing |
|---|---|---|---|
| Every 15–30 minutes | Every 15–30 minutes | Every 15 minutes | Every 5–15 minutes |
With intermittent auscultation , the nurse will also monitor uterine contractions by palpation. The nurse’s hand is placed at the top of the fundus prior to a contraction to determine baseline uterine tone. As the uterus contracts, the nurse feels a hardening of the uterus. The strength of the contraction is based on the laboring person’s description of the contraction and the nurse’s palpation. A mild contraction is similar to pressing on one’s cheek; a moderate contraction is similar to pressing on the tip of the nose; and a strong contraction is similar to pressing on the forehead. The nurse also notes the frequency and duration of the contraction during palpation.
Advantages and Disadvantages of Intermittent Auscultation
One advantage of IA is the freedom of movement it allows the laboring person. Movement in labor aids the fetus in its descent into the pelvis and in pain control for the laboring person. Because IA does not require attached monitors, the laboring person can walk, shower, sit on a birthing ball, or take a bath. The lack of monitors strapped onto the abdomen helps the laboring person rest easier between contractions.
One of the disadvantages of IA is the requirement for one-to-one nurse–laboring person staffing. This can be a challenge when the labor and delivery unit is busy and staffing is not available for one-to-one care. Another disadvantage is the lack of monitor tracings. Fetal monitor strips provide a visual history of the uterine contractions and FHR . These strips are used in communication with other health-care providers and provide a permanent record of labor.
Continuous External Monitoring of FHR and Contractions
The most common method of monitoring the fetal heart rate and contraction pattern is through continuous external monitoring . Doing so requires the use of two monitoring devices: an ultrasound device to evaluate the fetal heart rate, and a tocodynamometer (toco) to detect the frequency of uterine contractions. The nurse applies these external monitors to the patient’s abdomen; the devices are held in place with belts or adhesives. Figure 16.18 shows the continuous fetal monitor and the wireless fetal monitoring system. Wireless monitors allow patients to ambulate in labor. Other monitors are waterproof and allow for continuous monitoring during hydrotherapy and water birth.
Both transducers are connected to the monitor, and their signals are traced onto graph paper. The nurse explains to the patient that these monitors are external and can lose the signal with movement of the laboring person or fetus. The nurse explains that the laboring person should not be alarmed if they no longer see the signal on the monitor. They are instructed to call the nurse in these instances so that the monitor can be adjusted.
Through continuous external monitoring, fetal heart rate baseline and variability can be determined, as can periodic fetal heart rate changes. Situations requiring continuous fetal monitoring include meconium-stained fluid, multiple gestation, preeclampsia , epidural or spinal anesthesia, and dysfunctional labor (Simkin et al., 2017).
Application of the External Monitors
Uterine and FHR monitoring can be achieved externally and internally. After performing Leopold’s maneuvers , the nurse will place the external transducer and tocodynamometer on the person’s abdomen. The external monitors provide an FHR tracing.
Applying the Ultrasound Transducer
The ultrasound transducer is placed over the fetal back closest to the fetal head, where the FHR is usually the loudest. The nurse identifies this area using Leopold’s maneuvers as previously described. The transducer is not placed over the fetal chest because movement of the extremities interferes with continuous detection of the FHR. Ultrasound gel is placed on the transducer to allow a medium for ultrasound waves to travel into and out of the uterus. The transducer is then secured by a belt.
Placement of Uterine Tocodynamometer
The toco transducer senses change in the uterine muscle during a contraction. The toco transducer is placed on the abdomen where the fundus is firmest, most often over the fetal buttocks in a cephalic presentation. While performing Leopold’s maneuvers, the nurse can assess for the optimal placement of the toco. Having determined the optimal location, the nurse secures the toco transducer to the laboring person by a belt (Figure 16.19).
Advantages and Disadvantages of External Monitoring
The advantages of external fetal monitoring are its ease of use, the ability of the devices to record and digitally store the monitor results, and the ability for more advanced fetal assessment. This method also does not require one-on-one nurse staffing because the monitors are electronically connected to central monitors, which allow the nurse to read the fetal monitor tracing from any labor room or the nurses’ station and to monitor more than one patient simultaneously. Central monitoring also allows the nursing staff and health-care providers to assess the fetal monitor tracing from all rooms on the unit, from an office, and from home. Additionally, external monitors can be used regardless of the status of the amniotic membrane or the extent of cervical dilation.
A disadvantage of continuous external monitoring is that the required positioning of the monitor can result in the signal being lost when the person changes positions or gets out of bed. If wireless monitoring is not available, continuous monitoring can limit the pregnant person’s freedom to walk, shower, or bathe. Another disadvantage is that the tocodynamometer can determine only the frequency and duration of the contractions, but not the strength of the contractions, which will need to be palpated. As discussed previously, the nurse must palpate the uterus to evaluate the uterine contraction.
Continuous Internal Monitoring
Internal fetal monitors consist of the fetal scalp electrode (FSE) that affixes to the scalp of the fetus and provides close monitoring of the fetal heart rate and an intrauterine pressure catheter (IUPC) that lie inside the uterus and measure the frequency, duration, and strength of the uterine contractions and the resting tone of the uterus. The amniotic sac must be ruptured prior to placement of internal monitors. Nurses and health-care providers use internal monitors in situations that require more in-depth fetal surveillance, such as nonreassuring fetal heart rates , low amniotic fluid, and difficulty in maintaining a continuous FHR tracing, and during the use of uterotonics for labor induction or augmentation.
Application of Internal Monitors
In continuous internal monitoring , an FSE is attached to the fetal scalp, avoiding the fontanelles, and the IUPC is placed into the uterus between the fetus and uterine wall. Figure 16.20 illustrates the internal fetal monitoring system.
Internal monitors are placed by trained health-care providers and labor and birth nurses. A cervical exam is performed for assessment of dilation and membrane status. The cervix must be dilated, and the amniotic membrane must be ruptured to pass the monitors into the uterus. If the nurse assesses a need for internal monitoring, the nurse will notify the health-care provider. If the amniotic sac is intact, the health-care provider must determine the need for the monitors and weigh the pros and cons of rupturing the amniotic membrane. When appropriate, the health-care provider breaks the bag of amniotic fluid using an amniotomy hook , which is a plastic wand with a small hook that snags the membranes. Figure 16.21 illustrates use of the amniotomy hook.
Fetal Scalp Electrode
To place the fetal scalp electrode (FSE) , the fetal head must be low enough to be palpated during the vaginal exam, and the cervix must be open enough to insert the FSE. The head is assessed for suture lines and fontanelles, as seen in Figure 16.22. Avoiding the fontanelles, the nurse or the health-care provider places the scalp electrode firmly against the fetal scalp and turns it clockwise to adhere the electrode. The nurse then connects the scalp electrode transducer to the monitor, and the FHR electrocardiogram is detected and documented in the monitor tracing.
Intrauterine Pressure Catheter
The IUPC, seen in Figure 16.23, is inserted using a firm plastic introducer containing the pressure catheter. The catheter has markers to guide the depth of placement to avoid uterine perforation. To avoid the IUPC being inserted through the placenta, the introducer must be retracted immediately if frank red blood is noted. The pressure catheter transducer is attached to the monitor and traces, in exact millimeters of mercury ( mm Hg ), the strength of the contractions and the uterine resting tone.
Advantages and Disadvantages of Internal Monitoring
Internal monitors are an advantage when conditions are detected that require comprehensive and continuous evaluation of fetal well-being and uterine contractions. The fetal scalp electrode is the most precise way to monitor the fetal heart rate because it receives signals directly from the fetus and transmits them to the monitor tracing. In situations of FHR decelerations , the internal monitor can provide exact timing of the FHR deceleration in relation to the strength of contraction. The scalp electrode also allows the nurse to evaluate variability more precisely. This information is helpful in determining nursing interventions to resolve FHR decelerations. This monitor is also helpful when the FHR is difficult to detect with external monitors. In the situation where labor is not progressing as predicted, the IUPC can detect the strength of contractions. This information can assist the nurse in determining how to manage the oxytocin during labor induction or augmentation. Another advantage is that the health-care provider may use the FSE to rupture the membranes.
The disadvantages of internal monitors are increased risk of infection due to the rupture of membranes and the break in skin integrity necessary to place the fetal scalp electrode. Additionally, internal monitoring introduces the risk of injury to the fetus from the scalp electrode and the IUPC. During placement of the IUPC, there is a risk of puncturing the uterus and placenta, which is why the IUPC is inserted by the health-care provider or by registered nurses with advanced training in some labor and birth units.
Efficacy and Outcomes Data: Use of Continuous Electronic Fetal Monitoring
Continuous electronic fetal monitoring was developed in the 1970s. The original purpose of continuous electronic fetal monitoring was to decrease complications such as newborn seizures, cerebral palsy, and intrapartum fetal demise. According to the Cochrane Library (Alfirevic et al., 2017), continuous FHR monitoring with fetal scalp electrode , when compared to IA, showed no significant improvement in overall rate of fetal deaths but did significantly reduce the rate of neonatal seizures. The research found that intermittent versus continuous fetal scalp electrode monitoring did not increase instrumental or cesarean births, but no difference was seen in the incidence of cerebral palsy. Table 16.4 summarizes the advantages and disadvantages of the different fetal monitoring types.
| Monitor Type | Advantages | Disadvantages |
|---|---|---|
| Intermittent auscultation (IA) |
Freedom of mobility
Ability to shower or bathe Not dependent upon amniotic membrane status |
One-to-one nursing–pregnant person care
Lack of permanent record of FHR and UC |
| Continuous external |
Ease of use
Ability to record and store monitor results Allows the electronic fetal monitoring (EFM) to be read on any computer Not dependent upon amniotic membrane status |
Signal can be lost with movement of the fetus or person
Limits freedom of movement or hydrotherapy Toco does not provide strength of UC |
| Continuous internal |
More precise measurements of FHR and UC
Does not lose signal with movement of the fetus or person IUPC monitor results can help guide use of oxytocin |
Amniotic membrane must be ruptured
Increased risk for infection Risk of injury to the fetus or uterus from the FSE or IUPC devices |
Interpretation of the Electronic Fetal and Uterine Monitor Tracing
Interpretation of the fetal heart rate consists of evaluating the baseline, variability, and periodic changes of the FHR in relation to the uterine contractions. The nurse interprets uterine contractions by evaluating frequency, duration, strength, and resting tone. The contraction frequency is how often the contractions occur and is determined by measuring from the beginning of one contraction to the beginning of the next contraction. The contraction length is how long the contraction lasts and is determined by measuring the time between the beginning of the contraction and the end of the contraction. The contraction strength is the intensity of the contraction and is determined externally by palpation (see earlier discussion of intermittent auscultation ) or internally by the IUPC. Contraction strength cannot be measured accurately when the external toco is used; therefore, the nurse palpates and describes contractions as mild, moderate, or strong. When IUPC is in use, contractions will be described in mm Hg.
Interpreting fetal monitor tracings is a skill that takes practice to refine. This fetal monitoring game reviews fetal monitoring terminology and tracings. The game can be played unlimited times.
Expected uterine activity is defined as five contractions or fewer in a 10-minute period. Expected contraction length is between 45 and 60 seconds and may increase to 90 seconds closer to the onset of the second stage of labor. Abnormal uterine activity called uterine tachysystole is more than five contractions in 10 minutes or a contraction length of 2 or more minutes within a 30-minute period. Uterine tachysystole can be diagnosed in both spontaneous and induced labor.
Efficiency of the uterine contractions during labor can be measured in Montevideo units . The nurse calculates the Montevideo units by subtracting the uterine resting tone in mm Hg from the mm Hg measuring the peak of the contraction for each contraction occurring within a 10-minute time interval (Kissler et al., 2020). Montevideo units can be calculated only when an IUPC is in place.
Fetal well-being is influenced by uterine activity. Therefore, when the nurse is evaluating fetal well-being, both the fetal heart rate and uterine activity, as well as the fetal response to the uterine activity, must be described. A normal fetal monitor tracing is found in Figure 16.24.
Interpretation of fetal heart rate was historically a problem because of inconsistencies in terminology and reader error. In 2008, the National Institute of Child Health and Human Development Working Group created a three-tiered classification system to interpret fetal heart rate patterns (ACOG, 2009). The three-tiered system allows for consistent terminology and management by the health-care provider and nurse. A summary of the three categories is found in Figure 16.25.
Category I tracings are considered normal and do not require further actions by the nurse other than routine nursing care for the antepartum or laboring patient. Figure 16.26 shows a Category I tracing. Category II tracing characteristics do not meet the criteria of either Category I or III. Nursing care requires continued surveillance with consideration of clinical circumstances and reevaluation and notification of the health-care provider. Figure 16.27 shows a Category II tracing. Category III tracings are always considered abnormal and require the nurse to contact the health-care provider with a report of the FHR abnormalities. Nursing interventions aimed at resolving the cause of the abnormality are discussed in 16.5 Intrauterine Resuscitation in this chapter. If interventions do not resolve the abnormality, the birth must be expedited, most commonly via cesarean section (ACOG, 2009). Figure 16.28 shows a Category III tracing.
Documentation of the FHR and Uterine Contraction Pattern
Electronic health record ( EHR ) documentation during labor should include assessment of the pregnant person and the fetal heart rate. Continuous monitors record the fetal heart rate, and the tracings allow the nurse and health-care providers to review the current and previous tracing. The stored tracing also allows the nurse to care for the laboring patient during delivery and review the monitor tracing when needed.
Documentation should show evaluation of the fetal heart rate and contraction pattern every 15 to 30 minutes if there is continuous monitoring, with a summary of fetal status. The documentation should also discuss the frequency of assessment and the interpretation of the fetal heart rate. When labor-inducing medications are in use, such as oxytocin (Pitocin) , the nurse should document fetal status before and after increasing the dose (Simpson, 2014).
Documentation in labor is often determined by hospital policies. Every hospital should have a policy on the frequency of fetal heart rate and contraction pattern interpretation. To ensure all components of the tracing are documented, nurses use a standardized way of describing the FHR tracing. Figure 16.29 is an example of how to organize necessary information for documentation.
A process for evaluating and documenting fetal monitor tracings typically includes the following steps:
- Identify external or internal monitoring.
- Describe FHR baseline: rate and variability.
- Describe the presence or absence of FHR accelerations or decelerations.
- Identify the type of deceleration if present.
- Document the uterine contraction pattern with frequency, duration, intensity, and presence or absence of uterine resting tone.
- Interpret the tracing and identify the tracing as Category I, II, or III.
- Document the plan of care. Communication with the pregnant person and family is documented as part of the EHR . Nurses also document communication with the health-care provider and any new orders received from the provider.
Management of Uterine Tachysystole
Uterine tachysystole is defined as more than 5 contractions in 10 minutes averaged over 30 minutes. When administering oxytocin for induction or augmentation of labor, uterine tachysystole is a risk factor. The following interventions should be used when uterine tachysystole is diagnosed.
For uterine tachysystole with nonreassuring fetal heart rate pattern:
- Discontinue oxytocin.
- Turn laboring patient to lateral position.
- IV bolus with 500 mL lactated Ringer’s (unless contraindicated).
- Apply O 2 via mask at 8 to 10 liters per minute.
- Administer 0.25 mg terbutaline SQ.
For uterine tachysystole with reassuring fetal heart rate pattern:
- Reposition laboring patient (left or right lateral position).
- IV bolus with 500 mL lactated Ringer’s (unless fluid restricted).
- If uterine activity has not returned to normal after 10 minutes, decrease oxytocin rate by half; if uterine activity has not returned to normal after 10 minutes, discontinue oxytocin until uterine activity has returned to normal (≤ 5 contractions in 10 minutes).
- Notify the health-care provider.
- Have terbutaline 0.25 mg SQ readily available.
- If the tachysystole has resolved within 30 minutes, the oxytocin infusion may be restarted at ½ of the previous rate. If the tachysystole has resolved in > 30 minutes, the oxytocin infusion may be restarted at the previous rate.
(Lyndon & Wisner, 2021)