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Am Fam Physician. 2020;102(3):158-167

Patient information: See related handout on intrapartum fetal monitoring, written by the authors of this article.

This clinical content conforms to AAFP criteria for CME.

Author disclosure: No relevant financial affiliations.

Continuous electronic fetal monitoring was developed to screen for signs of hypoxic-ischemic encephalopathy, cerebral palsy, and impending fetal death during labor. Because these events have a low prevalence, continuous electronic fetal monitoring has a false-positive rate of 99%. The widespread use of continuous electronic fetal monitoring has increased operative and cesarean delivery rates without improved neonatal outcomes, but its use is appropriate in high-risk labor. Structured intermittent auscultation is an underused form of fetal monitoring; when employed during low-risk labor, it can lower rates of operative and cesarean deliveries with neonatal outcomes similar to those of continuous electronic fetal monitoring. However, structured intermittent auscultation remains difficult to implement because of barriers in nurse staffing and physician oversight. The National Institute of Child Health and Human Development terminology is used when reviewing continuous electronic fetal monitoring and delineates fetal risk by three categories. Category I tracings reflect a lack of fetal acidosis and do not require intervention. Category II tracings are indeterminate, are present in the majority of laboring patients, and can encompass monitoring predictive of clinically normal to rapidly developing acidosis. Presence of moderate fetal heart rate variability and accelerations with absence of recurrent pathologic decelerations provides reassurance that acidosis is not present. Category II tracing abnormalities can be addressed by treating reversible causes and providing intrauterine resuscitation, which includes stopping uterine-stimulating agents, fetal scalp stimulation and/or maternal repositioning, intravenous fluids, or oxygen. Recurrent deep variable decelerations can be corrected with amnioinfusion. Category III tracings are highly concerning for fetal acidosis, and delivery should be expedited if immediate interventions do not improve the tracing.

Continuous electronic fetal monitoring is the continuous monitoring of fluctuations of the fetal heart rate (FHR) in relation to maternal contractions and is considered standard practice during active labor.13 Continuous electronic fetal monitoring was developed for widespread use in the 1970s as a screening test for fetal hypoxia/acidosis during labor, specifically to reduce hypoxic-ischemic encephalopathy, cerebral palsy, and fetal death.13

Clinical recommendationEvidence ratingComments
Structured intermittent auscultation can be used for low-risk labor because it statistically decreases cesarean and operative vaginal delivery rates without increasing cerebral palsy or fetal death.1,14,16 BCochrane review of low-quality evidence and practice guidelines from the American College of Obstetricians and Gynecologists
The presence of moderate variability and/or accelerations is predictive of a lack of fetal acidosis.34,3638 CReviews of disease-oriented outcomes
Treat placental fetal perfusion through intrauterine resuscitation before proceeding to immediate delivery for all Category II or III tracings with concern for fetal acidosis.27,32,33 CGuidelines, with one small disease-oriented randomized controlled trial and one Cochrane review focusing on tocolytics aspect of intrauterine resuscitation
Perform amnioinfusion for recurrent variable decelerations to reduce the risk of cesarean delivery.42 BCochrane review of low-quality evidence
RecommendationSponsoring organization
Do not automatically initiate continuous electronic fetal heart rate monitoring during labor for women without risk factors; consider intermittent auscultation first.American Academy of Nursing

Fetal acidemia (pH < 7.15) is most accurately diagnosed via umbilical cord arterial sampling immediately after delivery.46 Because fetal acidosis can affect autonomic control and therefore variability of FHR, continuous electronic fetal monitoring is considered a surrogate marker for measurement.2,7 However, the very low prevalence of cerebral palsy (antepartum events are most likely causative agents), hypoxic-ischemic encephalopathy, and fetal death has led to a false-positive rate of 99%3 for continuous electronic fetal monitoring and a low predictive value.810 Additionally, continuous electronic fetal monitoring is falsely positive for fetal acidosis two-thirds of the time, with low sensitivity (57%) and specificity (69%).1,3 Furthermore, user variability in interpretation is high, with agreement between experts only half the time.11,12

Continuous electronic fetal monitoring includes external and internal monitoring.7 External monitoring involves placement of two monitors (one for FHR and the other for contractions) against the maternal abdomen. Internal monitoring involves intravaginal placement of monitors within the uterine cavity.7 A fetal scalp electrode is recommended for fetal heart monitoring when fetal position and/or maternal habitus make external monitoring suboptimal.4 External monitors measure only contraction frequency, but an intrauterine pressure catheter can also determine the strength of contractions.13 Placement of an intrauterine pressure catheter or fetal scalp electrode requires cervical dilation and amniotomy, which can increase the risk of intrauterine infection, fetal injury, and the transmission of herpes simplex virus and hepatitis B or C.4,13

Structured intermittent auscultation is a fetal monitoring option for detecting fetal acidosis in low-risk pregnancies.7,14,15 Typically, the labor nurse auscultates the fetal heartbeat with a handheld Doppler device (Table 1).7,1417 Structured intermittent auscultation is not standard practice in the United States because of 1:1 nursing staff requirements and physician oversight concerns, whereas continuous electronic fetal monitoring can be monitored centrally with continuous recording capabilities.7,1418

The clinician and the patient with a low-risk pregnancy discuss the benefits of structured intermittent auscultation vs. continuous electronic fetal monitoring; patient agreement to structured intermittent auscultation is documented in medical record; labor team ensures appropriate nurse staffing (1:1)
Labor nurse determines current fetal position and best location to place Doppler handheld probe (usually over the fetal back) with Leopold maneuvers; transabdominal ultrasonography (passive mode) can be used to identify the location of the fetal heart if manual palpation proves difficult
With one hand holding the probe in place, the other hand palpates the uterine fundus to detect maternal contractions
Following contractions, baseline fetal heart rate is assessed by counting the number of beats during a 30- to 60-second interval
For a minimum of 1 minute following contraction onset, fetal heart rate is reassessed at 6- to 10-second intervals to detect accelerations or decelerations in heart rate
Recommended frequency of structured intermittent auscultation during labor*
OrganizationLatent phaseActive phaseSecond stage

American College of Nurse-MidwivesNo recommendation15 to 30 minutes5 minutes
American College of Obstetricians and GynecologistsNo recommendation30 minutes15 minutes
Association of Women's Health, Obstetric and Neonatal NursesAt least hourly (< 4 cm cervical dilation)15 to 30 minutes (4- to 5-cm cervical dilation)5 to 15 minutes

Despite these challenges, structured intermittent auscultation should be considered for low-risk labor because it statistically decreases cesarean and operative vaginal delivery rates without an increase in unfavorable outcomes associated with continuous monitor use and a high false-positive rate.1,7,14,16,17 Compared with women who receive structured intermittent auscultation, those who receive continuous electronic fetal monitoring for an initial 20-minute period at admission are at increased risk of continuing use for the duration of their labor (relative risk [RR] = 1.30; 95% CI, 1.14 to 1.48; n = 10,753) and a possible 20% increased rate of cesarean delivery.19

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