Fetal Heart Rate Monitoring
Paul G. Tomich, M.D.
Department of Obstetrics and Gynecology
University of Nebraska College of Medicine
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)
“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
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
Ways to Monitor

Uterine contractions
 Fetal heart rate (FHR)
Ways to Monitor

Uterine contractions
 Fetal heart rate (FHR)
Features to Describe

Fetal heart rate (FHR)
– Top line on monitor strip

Uterine contractions
– Bottom line on
monitor strip
Features to Describe

Baseline
 Variability
 Accelerations
 Decelerations
 Trends over time
 Interpret into 1 of 3 categories
Baseline

Mean fetal heart rate
– Rounded to increments of 5
– During a 10 minute period
– Excluding accelerations and decelerations

Normal baseline
– 100-160 BPM
Baseline is RED LINE
Baseline

Bradycardia
<100 BPM

Tachycardia
>160 BPM

Indeterminate
– less than 2 minutes of baseline is present
Fetal Tachycardia

Normal variant
– prematurity

Intra-amniotic infection
 Fetal anemia
 Fetal cardiac arrhythmia (SVT)
 Fetal hypoxia
Features to Describe

Baseline
 Variability
 Accelerations
 Decelerations
 Trends over time
 Interpret into 1 of 3 categories
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
Variability
Features to Describe

Baseline
 Variability
 Accelerations
 Decelerations
 Trends over time
 Interpret into 1 of 3 categories
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
>15 beats above baseline
15 seconds to 2 minutes in length
Features to Describe

Baseline
 Variability
 Accelerations
 Decelerations

Trends over time
 Interpret into 1 of 3 categories
Decelerations

Decrease in baseline
 3 Types
– Early
– Variable
– Late
Deceleration

Decrease in FHR
Early Deceleration

Symmetrical to
contraction
 Mirror image of
contraction
 Gradual decrease in
FHR
– 30 secs or more from
onset to nadir
EARLY DECELERATION
 Gradual FHR decrease
 Onset to nadir 30 seconds or more
 Nadir of deceleration occurs with peak of contraction
 Mirror contraction
Late Decelerations

Deceleration is delayed in timing
– Occurs after the contraction

A gradual FHR decrease
– Onset to nadir > 30 second
Late Decelerations
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
Variable Declerations

Pathophysiology
– umbilical cord
compression
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
Sinusoidal Pattern

Smooth sin-wave pattern
 Cycle frequency 3-5 mins
 Persists for 20 minutes or
longer
Sinusoidal Pattern
Uterine Contractions

Number of contractions in 10 minutes
– averaged over thirty minutes

Document
– Frequency
– Intensity
– Duration
– Relaxation
 time between contractions
Monitoring of Contractions
Tachysystole

>5 contractions in 10 mins
– Averaged over 30 mins
Categorization of FHR Patterns

An evaluation of the fetus at a particular point in
time
 Categories I, II, and III
3 Categories
Category I

Normal baseline
– 110-160 BPM

FHR Variability
– moderate

Late or Variable decelerations
– none
Category II

Not enough evidence to place into
either Category I or III
Category III

Abnormal tracing
 Predictive of abnormal fetal acid-base status
 Requires prompt intervention
The ABCD’s of Fetal Monitoring
Examples of Tracings
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
•
Reactive NST
Biophysical Profile (BPP)

NST + ultrasound markers
 Score linearly correlated with fetal pH
 Risk of fetal death within one week of normal
BPP is 1:1300
Biophysical Profile
•Zero
or 2 points for each
•Fetal heart beat monitor
•Fetal breathing
•Fetal movements
•Amniotic Fluid Volume
•Flexion/Extension
Modified Biophysical Profile
•Combination of
•If
NST and AFI only
less than 4/4
•more evaluation is done
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