• Identify typical signs of normal (reassuring) and abnormal (nonreassuring) fetal heart rate (FHR) patterns. • Compare FHR monitoring performed by intermittent auscultation with external and internal electronic methods. • Explain the baseline FHR and evaluate periodic changes. • Describe nursing measures that can be used to maintain FHR patterns within normal limits. • Differentiate among the nursing interventions used for managing specific FHR patterns, including tachycardia and bradycardia, absent or minimal variability, and late and variable decelerations. • Review the documentation of the monitoring process necessary during labor. Additional related content can be found on the companion website at evolve.elsevier.com/Lowdermilk/Maternity/ • Critical Thinking Exercise: Fetal Monitoring • Nursing Care Plan: Electronic Fetal Monitoring during Labor T he ability to assess the fetus by auscultation of the fetal heart was initially described more than 300 years ago. With the advent of the fetoscope and stethoscope after the turn of the twentieth century the listener could hear clearly enough to count the fetal heart rate (FHR). When electronic FHR monitoring made its debut for clinical use in the early 1970s, the anticipation was that its use would result in fewer cases of cerebral palsy and be more sensitive than stethoscopic auscultation in predicting and preventing fetal compromise (Garite, 2007). Consequently, the use of electronic fetal monitoring rapidly expanded. However, the rate of cerebral palsy has risen slightly since that time and is not likely to improve (Gilbert, 2007). Moreover, in 2006 the cesarean birth rate in the United States reached an all-time high of 31.1% (Collard, Diallo, Habinsky, Hentschell, & Vezeau, 2008/2009). Still, electronic fetal monitoring (EFM) is a useful tool for visualizing FHR patterns on a monitor screen or printed tracing and continues to be the primary mode of intrapartum fetal assessment. Currently in the United States, approximately 85% of women giving birth have continuous EFM during labor, making it the most commonly performed obstetric procedure (American College of Obstetricians and Gynecologists [ACOG], 2009; Tucker, Miller, & Miller, 2009). Pregnant women should be informed about the equipment and procedures used and the risks, benefits, and limitations of intermittent auscultation (IA) and EFM. This chapter discusses the basis for intrapartum fetal monitoring, the types of monitoring, and nursing assessment and management of abnormal fetal status. • Reduction of blood flow through the maternal vessels as a result of maternal hypertension (chronic hypertension, preeclampsia, or gestational hypertension), hypotension (caused by supine maternal position, hemorrhage, or epidural analgesia or anesthesia), or hypovolemia (caused by hemorrhage) • Reduction of the oxygen content in the maternal blood as a result of hemorrhage or severe anemia • Alterations in fetal circulation, occurring with compression of the umbilical cord (transient, during uterine contractions [UCs], or prolonged, resulting from cord prolapse), placental separation or complete abruption, or head compression (head compression causes increased intracranial pressure and vagal nerve stimulation with an accompanying decrease in the FHR) • Reduction in blood flow to the intervillous space in the placenta secondary to uterine hypertonus (generally caused by excessive exogenous oxytocin) or secondary to deterioration of the placental vasculature associated with maternal disorders such as hypertension or diabetes mellitus • A baseline FHR rate of 110 to 160 beats/min • Moderate baseline FHR variability • Late or variable decelerations absent • Early decelerations present or absent Table 11-1 describes normal uterine activity (UA) during labor. TABLE 11-1 Normal Uterine Activity during Labor Source: Tucker, S. M., Miller, L. A, & Miller, D. A. (2009). Mosby’s pocket guide to fetal monitoring: A multidisciplinary approach (6th ed.). St. Louis: Mosby. Intermittent auscultation (IA) involves listening to fetal heart sounds at periodic intervals to assess the FHR. IA of the fetal heart can be performed with a Pinard stethoscope, a Doppler ultrasound device (Fig.11-1, A) an ultrasound stethoscope (Fig. 11-1, B) or a DeLee-Hillis fetoscope (Fig. 11-1, C). The fetoscope is applied to the listener’s forehead because bone conduction amplifies the fetal heart sounds for counting. The Doppler ultrasound device and ultrasound stethoscope transmit ultrahigh-frequency sound waves reflecting movement of the fetal heart and convert these sounds into an electronic signal that can be counted. Box 11-1 describes how to perform IA. IA is easy to use, inexpensive, and less invasive than EFM. It is often more comfortable for the woman and gives her more freedom of movement. Other care measures, such as ambulation and the use of baths or showers, are easier to carry out when IA is used. On the other hand, IA may be difficult to perform in women who are obese. Because IA is intermittent, significant events may occur during a time when the FHR is not auscultated. Also, IA does not provide a permanent documented visual record of the FHR and cannot be used to assess visual patterns of the FHR variability or periodic changes (Albers, 2007; Tucker et al., 2009). By using IA the nurse can assess the baseline FHR, rhythm, and increases and decreases from baseline. The recommended optimal frequency for IA in low risk women during labor has not been determined (Nageotte & Gilstrap, 2009). TABLE 11-2 External and Internal Modes of Monitoring The external transducer is easily applied by the nurse, but it must be repositioned as the woman or fetus changes position (see Fig. 11-2, B). The woman is asked to assume a semi-sitting or a lateral position. Use of an external transducer confines the woman to bed. Portable telemetry monitors allow observation of the FHR and UC patterns by means of centrally located electronic display stations. These portable units permit the woman to walk around during electronic monitoring. In April 2008 the NICHD, ACOG, and the Society for Maternal-Fetal Medicine partnered to sponsor another workshop to revisit the FHR definitions recommended by the NICHD in 1997. The 1997 FHR definitions were reaffirmed at this workshop. In addition, new definitions related to UA were recommended, as well as a three-tier system of FHR pattern interpretation and categorization (Macones et al., 2008). ACOG (2009) has recently published a practice bulletin which supports use of the 2008 NICHD workshop recommendations. The baseline fetal heart rate is the average rate during a 10-minute segment that excludes periodic or episodic changes, periods of marked variability, and segments of the baseline that differ by more than 25 beats/min (Macones et al., 2008). The normal range at term is 110 to 160 beats/min. The baseline rate is documented as a single number, rather than a range (Tucker et al., 2009). Variability of the FHR can be described as irregular waves or fluctuations in the baseline FHR of two cycles per minute or greater (Macones, et al., 2008). It is a characteristic of the baseline FHR and does not include accelerations or decelerations of the FHR. Variability is quantified in beats per minute and is measured from the peak to the trough of a single cycle. Four possible categories of variability have been identified: absent, minimal, moderate, and marked (Fig. 11-5). In the past, variability was described as either long term or short term (beat to beat). The NICHD definitions do not distinguish between long- and short-term variability, however, because in actual practice, they are visually determined as a unit (NICHD, 1997).
Fetal Assessment during Labor
Web Resources
Basis for Monitoring
Fetal Response
Uterine Activity
CHARACTERISTIC
DESCRIPTION
Frequency
Contraction frequency overall generally ranges from two to five per 10 minutes during labor, with lower frequencies seen in the first stage of labor and higher frequencies (up to five contractions in 10 minutes) seen during the second stage of labor.
Duration
Contraction duration remains fairly stable throughout the first and second stages, ranging from 45-80 seconds, not generally exceeding 90 seconds.
Intensity (peak less resting tone)
Intensity of uterine contractions generally range from 25-50 mm Hg in the first stage of labor and may rise to over 80 mm Hg in second stage. Contractions palpated as “mild” would likely peak at less than 50 mm Hg if measured internally, whereas contractions palpated as “moderate” or greater would likely peak at 50 mm Hg or greater if measured internally.
Resting tone
Average resting tone during labor is 10 mm Hg; if using palpation, should palpate as “soft” (i.e., easily indented, no palpable resistance).
Montevideo units (MVUs)
Ranges from 100-250 MVUs in the first stage, may rise to 300-400 in the second stage. Contraction intensities of 40 mm Hg or more and MVUs of 80-120 are generally sufficient to initiate spontaneous labor.
Monitoring Techniques
Intermittent Auscultation
Electronic Fetal Monitoring
EXTERNAL MODE
INTERNAL MODE
FETAL HEART RATE
Ultrasound transducer: High-frequency sound waves reflect mechanical action of the fetal heart. Noninvasive. Does not require rupture of membranes or cervical dilation. Used during both the antepartum and intrapartum periods.
Spiral electrode: Converts the fetal ECG as obtained from the presenting part to the FHR via a cardiotachometer. Can be used only when membranes are ruptured and the cervix is sufficiently dilated during the intrapartum period. Electrode penetrates into fetal presenting part by 1.5 mm and must be attached securely to ensure a good signal.
UTERINE ACTIVITY
Tocotransducer: Monitors frequency and duration of contractions by means of pressure-sensing device applied to the maternal abdomen. Used during both the antepartum and intrapartum periods.
Intrauterine pressure catheter (IUPC): Monitors the frequency, duration, and intensity of contractions. The two types of IUPCs are a fluid-filled system and a solid catheter. Both measure intrauterine pressure at the catheter tip and convert the pressure into millimeters of mercury on the uterine activity panel of the strip chart. Both can be used only when membranes are ruptured and the cervix is sufficiently dilated during the intrapartum period.
External monitoring
Internal monitoring
Fetal Heart Rate Patterns
Baseline Fetal Heart Rate
Variability
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Fetal Assessment during Labor
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