What are the guidelines for fetal heart monitoring during labor?

Guidelines for Fetal Heart Monitoring During Labor

For low-risk pregnancies, structured intermittent auscultation is equivalent to continuous electronic fetal monitoring (EFM) in detecting fetal compromise, while continuous EFM increases cesarean sections and instrumental deliveries without improving most neonatal outcomes except for reducing neonatal seizures. 1

Choosing the Monitoring Method

Structured Intermittent Auscultation (SIA)

SIA is appropriate for low-risk patients and requires a 1:1 nurse-to-patient ratio with established institutional protocols. 1

Frequency of auscultation: 1

• Every 15-30 minutes during the active phase of first stage of labor
• Every 5 minutes during second stage of labor with pushing

Proper SIA technique includes: 1

• Palpate abdomen to determine fetal position (Leopold maneuvers)
• Place Doppler over area of maximal intensity of fetal heart tones
• Differentiate maternal from fetal pulse
• Palpate for uterine contractions during auscultation
• Count FHR between contractions for ≥60 seconds to determine baseline rate
• Count FHR after uterine contraction for 60 seconds to identify fetal response

Critical caveat: Current SIA methodology may miss late decelerations because many reach their nadir before the contraction ends, meaning auscultation after the contraction may capture only the recovery phase. 2, 3 Consider auscultating before and after contractions to establish a true baseline and detect late decelerations more reliably. 2

Continuous Electronic Fetal Monitoring (EFM)

Continuous EFM is indicated for: 1

• High-risk patients (see Table 2 in source)
• Abnormalities detected during structured intermittent auscultation
• Chorioamnionitis or other intrapartum complications

Important outcomes of continuous EFM versus SIA: 1

• Reduces neonatal seizures (NNT = 661) but does not reduce cerebral palsy or overall neonatal death
• Increases cesarean delivery rates (NNH = 20)
• Increases instrumental vaginal births (NNH = 33)

Avoid routine admission EFM tracings in low-risk pregnancies as they increase interventions without improving neonatal outcomes (increased epidural analgesia NNH = 19, continuous EFM NNH = 7, fetal scalp testing NNH = 45). 1

Interpreting Continuous EFM: The DR C BRAVADO Approach

Use the systematic DR C BRAVADO mnemonic for interpretation: 1

• DR (Determine Risk): Assess clinical risk status (low, medium, high)
• C (Contractions): Rate, rhythm, frequency, duration, intensity, resting tone
• BRA (Baseline Rate): Normal 110-160 bpm; bradycardia <110 bpm; tachycardia >160 bpm
• V (Variability): Absent, minimal, moderate (reassuring), or marked
• A (Accelerations): Spontaneous or stimulated; ≥15 bpm for ≥15 seconds (≥10 bpm for ≥10 seconds if preterm)
• D (Decelerations): Absent, early, variable, late, or prolonged
• O (Overall Assessment): Categorize and implement management plan

Contraction Assessment

Normal contractions are defined as ≤5 contractions per 10-minute period, averaged over 30 minutes. 1, 4 More than 5 contractions per 10 minutes is classified as tachysystole (the term "hyperstimulation" should be abandoned). 1 Tachysystole must be qualified by presence or absence of FHR decelerations. 4

Use an intrauterine pressure catheter (IUPC) if accurate assessment of contraction strength is clinically necessary, as external transducers cannot reliably measure amplitude. 1, 4

NICHD Three-Tier Classification System

Category I (Normal) 1, 5

• Moderate baseline FHR variability, no late or variable decelerations
• Indicates normal pH and fetal well-being
• Management: Continue current monitoring method (SIA or continuous EFM)

Category II (Indeterminate) 1

This encompasses all tracings not in Category I or III and requires clinical judgment:

For baseline rate changes:

• Tachycardia: Consider medication effects, maternal anxiety, infection, fever
• Bradycardia: Consider rupture of membranes, occipitoposterior position, post-term pregnancy

For variability changes (absent, minimal, or marked):

• May indicate medications, sleep cycle, monitoring technique issues, or possible fetal hypoxia
• Consider changing monitoring method or using internal monitoring

For decelerations without absent variability:

• Variable decelerations: Consider cord entrapment; use amnioinfusion for recurrent decelerations (reduces cesarean delivery NNT = 8, improves multiple neonatal outcomes) 1
• Late decelerations: Consider uteroplacental insufficiency, epidural hypotension, tachysystole

General interventions for Category II tracings: 1

• Vaginal examination (check for cord prolapse, rapid descent, bleeding)
• Check maternal vital signs
• Administer oxygen at 6-10 L/min
• Change maternal position
• Administer IV fluids or bolus
• Discontinue oxytocin if in use
• Consider fetal scalp or acoustic stimulation to assess pH
• Consider expedited delivery if abnormalities persist

Category III (Abnormal) 1

• Absent baseline FHR variability with recurrent decelerations (variable or late) and/or bradycardia
• Sinusoidal FHR pattern
• Indicates uteroplacental insufficiency, fetal hypoxia or acidemia
• Management: Discontinue oxytocin and expedite delivery (operative vaginal or cesarean)

Adjunctive Technologies

Fetal electrocardiography analysis added to EFM reduces operative vaginal deliveries (NNT = 50) and fetal scalp sampling (NNT = 33). 1

Fetal pulse oximetry has not shown reduction in cesarean delivery rates and is not recommended. 1

If absent or minimal variability without spontaneous accelerations is present, an acceleration after scalp or acoustic stimulation indicates fetal pH ≥7.20. 1

Monitoring During Labor

For continuous EFM: 1

• Check maternal blood pressure every 5 minutes for 15 minutes after initial bolus and after each subsequent intervention
• Check sensory and motor block hourly
• Continuous fetal heart rate monitoring should be employed throughout labor when using neuraxial analgesia or intrathecal catheters due to increased risk of fetal bradycardia with intrathecal opioids

Common Pitfalls to Avoid

Do not confuse a temporarily reassuring tracing with sustained reassurance - continue regular assessment even with Category I tracings. 5

Avoid unnecessary interventions for truly Category I tracings, as this increases cesarean rates without improving outcomes. 5

Remember that current SIA technique may miss late decelerations if auscultation occurs only after contractions during the recovery phase. 2, 3

Do not rely on contraction patterns alone to assess labor progress - serial cervical examinations remain the gold standard. 4

Ensure proper staffing ratios (1:1) when using SIA, as safety depends on adequate nursing resources. 1