Fetal Heart Rate Monitoring

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Fetal Heart Rate Monitoring

• Paul G. Tomich, M.D.
• Department of Obstetrics and Gynecology
• University of Nebraska College of Medicine

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Learning Objectives

• Evolution
• Examples
• Descriptions
• Reassuring patterns
• Concerning patterns
• Definitions of Category I, II, and III tracings
• Discuss action needed
• Non-stress Test (NST)
• Biophysical Profile (BPP)

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Evolution of FHR Monitoring

• Monitoring fetus in labor
• FHR patterns
• Good outcomes
• Poor outcomes
• Contraction Stress Test (CST)
• Non Stress Test (NST)
• Biophysical profile (BPP)
• Categorization of FHR Tracing into Category I,
  II, and III

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Categorization of FHR Tracings

• Recommendation of three-tiered system
• April 2008
• More standardized interpretation
• Concept Interpretation of a FHR monitor strip is
  a dynamic process, with determination of whether
  a particular strip is reassuring and what action
  plans should be taken and then to evaluate at a
  later time

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Ways to Monitor

• Uterine contractions
• Fetal heart rate (FHR)

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Ways to Monitor

• Uterine contractions
• Fetal heart rate (FHR)

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Features to Describe

• Fetal heart rate (FHR)
• Top line on monitor strip
• Uterine contractions
• Bottom line on
• monitor strip

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Features to Describe

• Baseline
• Variability
• Accelerations
• Decelerations
• Trends over time
• Interpret into 1 of 3 categories

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Baseline

• Mean fetal heart rate
• Rounded to increments of 5
• During a 10 minute period
• Excluding accelerations and decelerations
• Normal baseline
• 100-160 BPM

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Baseline is RED LINE
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Baseline

• Bradycardia
• lt100 BPM
• Tachycardia
• gt160 BPM
• Indeterminate
• less than 2 minutes of baseline is present

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Fetal Tachycardia

• Normal variant
• prematurity
• Intra-amniotic infection
• Fetal anemia
• Fetal cardiac arrhythmia (SVT)
• Fetal hypoxia

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Features to Describe

• Baseline
• Variability
• Accelerations
• Decelerations
• Trends over time
• Interpret into 1 of 3 categories

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Variability

• Fluctuations in FHR
• Over 10 minutes
• Descriptors are
• Absent undetectable amplitude range
• Minimal undetectable up to 5 BPM
• Moderate amplitude range 6 to 25 BPM
• Marked amplitude range greater than 25 BPM

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Variability
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Features to Describe

• Baseline
• Variability
• Accelerations
• Decelerations
• Trends over time
• Interpret into 1 of 3 categories

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Accelerations

• Abrupt increase in FHR
• At least 15 BPM above baseline
• Duration
• Must last 15 seconds to 2 minutes
• Prolonged accelerations
• Last 2 minutes to 10 minutes
• Baseline change
• Acceleration lasting 10 mins or longer

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gt15 beats above baseline 15 seconds to 2 minutes
in length
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Features to Describe

• Baseline
• Variability
• Accelerations
• Decelerations
• Trends over time
• Interpret into 1 of 3 categories

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Decelerations

• Decrease in baseline
• 3 Types
• Early
• Variable
• Late

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Deceleration

• Decrease in FHR

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Early Deceleration

• Symmetrical to contraction
• Mirror image of contraction
• Gradual decrease in FHR
• 30 secs or more from onset to nadir

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• EARLY DECELERATION
• Gradual FHR decrease
• Onset to nadir 30 seconds or more
• Nadir of deceleration occurs with peak of
  contraction
• Mirror contraction

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Late Decelerations

• Deceleration is delayed in timing
• Occurs after the contraction
• A gradual FHR decrease
• Onset to nadir gt 30 second

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Late Decelerations
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Variable Decelerations

• Abrupt decrease in fetal heart rate
• Onset to nadir less than 30 seconds
• Decrease in FHR
• 15 BPM or more
• Lasting 15 seconds to 2 mins

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Variable Declerations

• Pathophysiology
• umbilical cord compression

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Decelerations

• Prolonged deceleration
• Decrease of 15 BPM
• Lasts 2-10 minutes
• Baseline change
• Deceleration lasting at least 10 mins
• Description
• Intermittent
• Less than 50 of contractions in 20 minutes
• Recurrent
• More than 50 of contractions in 20 minutes

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Sinusoidal Pattern

• Smooth sin-wave pattern
• Cycle frequency 3-5 mins
• Persists for 20 minutes or longer

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Sinusoidal Pattern
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Uterine Contractions

• Number of contractions in 10 minutes
• averaged over thirty minutes
• Document
• Frequency
• Intensity
• Duration
• Relaxation
• time between contractions

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Monitoring of Contractions
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Tachysystole

• gt5 contractions in 10 mins
• Averaged over 30 mins

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Categorization of FHR Patterns

• An evaluation of the fetus at a particular point
  in time
• Categories I, II, and III

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3 Categories
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Category I

• Normal baseline
• 110-160 BPM
• FHR Variability
• moderate
• Late or Variable decelerations
• none

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Category II

• Not enough evidence to place into either Category
  I or III

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Category III

• Abnormal tracing
• Predictive of abnormal fetal acid-base status
• Requires prompt intervention

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The ABCDs of Fetal Monitoring
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Examples of Tracings
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Non-Stress Test

• Reactive
• 2 or more accelerations in 20 mins
• Acceleration
• At least 15 beats above baseline
• Lasting for at least 15 seconds
• Non-reactive

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Reactive NST
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Biophysical Profile (BPP)

• NST ultrasound markers
• Score linearly correlated with fetal pH
• Risk of fetal death within one week of normal BPP
  is 11300

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Biophysical Profile

• Zero or 2 points for each
• Fetal heart beat monitor
• Fetal breathing
• Fetal movements
• Amniotic Fluid Volume
• Flexion/Extension
• Fetal Monitoring 4 accelerations in
  40 minutes
• Fetal Breathing 30 seconds
• Fetal Movements Truncal
• Flexion/Extension Arm/leg activity
• Amniotic Fluid AFI gt 5.0 cm
• BPP of 8/10 or 10/10 is normal or reassuring
• BPP of 6/10 requires some sort of intervention

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Modified Biophysical Profile

• Combination of NST and AFI only
• If less than 4/4
• more evaluation is done

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Guidelines for Reviewing FHR Monitoring

• normal patient
• reviewed every 30 min in the first stage of
  labor
• every 15 minutes in the second stage
• complicated patients
• every 15 minutes in first stage
• Every 5 mins in second stage