External Fetal Monitoring
• Computer assisted auditory & visual
assessment of fetal heart rate (FHR)
and uterine contractions (UC)
• Components:
– Tocotransducer: placedover
fundus
– Ultrasound transducer: placed
over fetal back
External Fetal Monitoring
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Advantages
Dilation/ ROM not needed
Nonninvasive
Easy to apply
Continuous tracing of FHR
Frequency of UCs easily assessed
FHR changes detected early.
No complications associated with use.
External Fetal Monitoring
Disadvantages
• Reliable tracing difficult if patient obese or active
• May pick up artifact
• FHR may be lost if fetus active or changes
position
• FHR may only be picked up when woman on back
• No information about intensity of the contractions;
fundus must be palpated to assess intensity.
• Cannot determine baseline tone of uterus
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Internal Fetal Monitoring
• Intrauterine pressure catheter (IUPC) with pressure
gauge on one end
– Inserted via cervix into amniotic fluid in uterus
– Intrauterine pressure measured in mm Hg
– Must be 2-3 cm dilated with ruptured membranes
• Fetal Scalp Electrode (FSE) spiral electrode
– Inserted via cervix; attached to presenting part
giving direct EKG.
– Must be 2 cm dilated with ruptured membranes
– Thick fetal hair may make insertion difficult
Internal Fetal Monitoring
Advantages
• Freedom of movement without altering quality of
tracing
• Accurately measures about intensity of Ucs and
baseline tone( in mm Hg)
• FHR variability can be assessed
• Can cultures of amniotic fluid through lumen
• Can instill fluid into uterus; amnioinfusion
• Not usually subject to artifact
Internal Fetal Monitoring
Disadvantages
• Requires partial dilation of cervix
• Requires skilled to apply scalp electrode and insert
IUPC.
• Insertion of IUPC and FSE uncomfortable
• Requires sterile, disposable equipment
• IUPC may be impossible to insert if fetus at low
station
• Complications: scalp abscess or laceration, uterine
perforation, separation of a low-lying placenta,
bleeding
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Monitor Strip Literacy
Two sections:
– Upper is where FHR appears
– Lower is where uterine activity appears
Monitor Strip: Fetal Heart Graph
Longitudinal
• Divided into 10 sec intervals by light line. Every 6th line
dark. Time between two dark lines = 1 min
Horizontal
• Divided horizontally by lines with a column of numbers
ranging from 30 to 240. These numbers to determine the
FHR and represent beats per minute.
Monitor Strip: Contraction Graph
Longitudinal
• Divided vertically by lines. Time between two dark
lines = 1 min. Time between two light lines = 10 sec
Horizontal
• Column of numbers from 0 to 100; determine the
intensity of UCs when a pressure catheter is used
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Uterine Contractions
Four Phases of UC pattern
Increment: the building up phase; longest part
Acme: peak; shortest & most intense part
Decrement: letting up phase; diminishing of contraction
Nadir: resting phase; facilitates uteroplacental
reoxygenation
Uterine Contractions
Duration: length of UC, measured from beginning of
increment to end of decrement
Frequency: from onset of one UC to onset of the next UC
Intensity: the strength of the contraction during acme,
measured by palpation as mild, moderate, or strong or by
IUPC
Montevideo Units
• Way to describe uterine intensity when IUPC is used
• To calculate:
– Baseline uterine pressure subtracted from the
peak contraction pressure for each UC recorded
in a 10 min tracing
– These adjusted pressures are added together and
the sum is the number of MVUs
• Average is 180 to 240
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EFM-Fetal Heart Rate
• External
– Ultrasound transducer placed over fetal back detects
fetal heart movement.
– Maternal obesity, fetal or maternal movement may
interfere
• Internal
– Fetal scalp electrode inserted through cervix and
attached to epidermis of presenting part giving direct
EKG.
– Must be dilated to at least 2 cm with ruptured
membranes.
– Thick fetal hair may make insertion difficult on
cephalic presentation
EFM-Fetal Heart Rate
• Baseline FHR
– Average heart rate between UCs; measured in bpm.
– Normal range is 120-160
• Short-term variability
– Change in rate between one beat and the next creating
a jagged appearance
– Interplay of fetal sympathetic/parasympathetic NS
– Decreased by fetal tachycardia, prematurity, fetal heart
and CNS anomalies and fetal sleep
– Normal is 2 to 3 bpm; classified as present or absent
– Can only be evaluated by internal monitoring?
EFM-Fetal Heart Rate
• Long-term variability
– Rhythmic fluctuations occurring 2 to 6 times per
minute; wave-like
– Determined by interplay between fetal SNS/PNS
– Increased by fetal movement
– Decreased by fetal sleep or hypoxia and subsequent
acidosis
– Average or moderate is 6 to 25 bpm
– Minimal or decreased = < 6
– Marked or increased = > 25
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Fetal Tachycardia
Baseline increase > 160
May result from:
• Hypoxia
• Drugs
• Prematurity
• Maternal fever
• Fetal infection
• Fetal tachyarrhythmia
• Maternal hyperthyroidism
• Fetal movement
Fetal Bradycardia
Decrease in baseline FHR < 120 BPM
May result from:
• Fetal hypoxia:
• Drugs
• Umbilical cord compression
• Maternal hypotension
• Fetal cardiac arrhythmias
• Maternal hypothermia
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FHR Periodic Changes
• Periodic FHR Changes: deviations from baseline
occurring with UCs
• Episodic FHR changes: deviations from baseline
occurring independently from UCs
• Accelerations:transient increases in FHR
– Episodic (spontaneous): symmetric, uniform, not r/t
UCs, occur in response to fetal movement, indicate
fetal well-being
– Periodic: occur with UC
Periodic Accelerations
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Begins with UC; returns to baseline at end of UC
Height of acceleration reflects intensity of UC
Occurs repeatedly throughout labor
Occur most frequently in following situations:
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Preterm labor
Term breech
During vaginal examinations
During abdominal palpation
Active fetus
• No treatment required
Early Decelerations
• FHR decrease: begins onset of UC and returns to
baseline by end of UC with lowest point of
deceleration at UC acme
• Uniform shape inversely mirrors contraction
• Cause: fetal head compression and vagus nerve
stimulation
• Rarely falls below 110 BPM
• Associated with vaginal exams, FSE application,
CPD, after AROM, vetex positions
• No intervention required
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Late Decelerations
• Begins after UC onset and returns to baseline after
end of UC
• Uniform shape
• Cause: uteroplacental insufficiency
• Considered ominous
• Nursing interventions:
– Oxygenate: O2 by mask at 8-10 LPM
– Rotate: Lateral position to improve perfusion
– Hydrate: Increase IV fluid rate
– Discontinue oxytocin if infusing
– Call healthcare provider
Variable Decelerations
• Variable in duration and intensity
• Variable in relation to UCs (variable in onset and
return to baseline)
• Variable shape, usually “U”, “V” or “W”
• Variable in depth
• Variable in duration
• Begin and resolve abruptly
• Caused by compression of umbilical cord
• Often seen in late labor
Variable Decelerations
• Classified as mild, moderate or severe based on lowest
FHR reading and duration of deceleration
– Mild: decelerates to any level for < 30 sec with
abrupt return to baseline
– Moderate: decelerates no lower than 80 BPM for any
duration with abrupt return to baseline
– Severe: decelerates < 60 BPM for > 60 sec with slow
return to baseline ( ominous; indicate fetal asphyxia)
• Nursing interventions: relieving cord compression
through repositioning, vaginal exam for prolapsed cord,
oxygen by mask, assist with amnioinfusion
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