Fetal Heart Rate Monitoring

Paul G. Tomich, M.D.

Department of Obstetrics and Gynecology

University of Nebraska College of Medicine

Learning Objectives

EvolutionExamplesDescriptions

– 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 laborFHR 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

Uterine contractionsFetal heart rate (FHR)

Ways to Monitor

Uterine contractionsFetal heart rate (FHR)

Ways to Monitor

Features to DescribeFetal heart rate (FHR)

– Top line on monitor stripUterine contractions

– Bottom line on

monitor strip

Features to DescribeBaselineVariabilityAccelerationsDecelerationsTrends over timeInterpret 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

Bradycardia<100 BPM

Tachycardia>160 BPM

Indeterminate– less than 2 minutes of baseline is present

Baseline

Fetal Tachycardia

Normal variant– prematurity

Intra-amniotic infectionFetal anemiaFetal cardiac arrhythmia (SVT)Fetal hypoxia

Features to DescribeBaselineVariabilityAccelerationsDecelerationsTrends over timeInterpret 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 DescribeBaselineVariabilityAccelerationsDecelerationsTrends over timeInterpret 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 baseline15 seconds to 2 minutes in length

Features to DescribeBaselineVariabilityAccelerationsDecelerationsTrends over timeInterpret into 1 of 3 categories

Decelerations

Decrease in baseline3 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 secondsDecrease in FHR

– 15 BPM or more– Lasting 15 seconds to 2

mins

Variable Declerations

Pathophysiology– umbilical cord

compression

DecelerationsProlonged 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 patternCycle frequency 3-5 minsPersists 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 tracingPredictive of abnormal fetal acid-base statusRequires 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

NST + ultrasound markersScore linearly correlated with fetal pHRisk of fetal death within one week of normal

BPP is 1:1300

Biophysical Profile (BPP)

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 > 5.0 cm

•BPP of 8/10 or 10/10 is “normal” or “reassuring”•BPP of 6/10 requires some sort of intervention

Modified Biophysical Profile

•Combination of NST and AFI only•If 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