Prepared by Helen Cooke

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Intrapartum Fetal Heart Rate Monitoring
Prepared by Helen Cooke Warwick Giles February
2008
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Goals

• Who should be monitored
• Tools for intrapartum monitoring
• Describe the parameters for intrapartum assessment

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FHR as a screening test

• Intrapartum FHR monitoring is a screening test
  that provides information to alert the clinician
  that a true test for fetal welfare assessment
  needs to be performed, eg
• An atypical variable (pathological feature)
• fetal blood sampling should be performed

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Documentation

• At commencement of the CTG the documentation of
  the pattern should include
• womans name and MRN,
• estimated gestational age,
• clinical indications for performing the FHR
  pattern,
• time and date of commencement and
• maternal pulse rate.
• The outcome of the FHR pattern should be
  documented both on the CTG and in the womans
  medical records at least every ½ hourly
  throughout labour.

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FHR evaluation

• Dr C Bravado ? ALSO
• DR determine the risk
• C contractions
• Bra baseline rate
• V variability
• A accelerations
• D decelerations
• O overall assessment (followed by a management
  plan)

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FHR Monitoring on admission in labour

• ??? Electronic FHR monitoring
• ??? Doppler auscultation
• ??? Pinards

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Considerations for which form of monitoring to
use on admission

• Has the woman had good antenatal care?
• Are you aware of the fetal welfare and
  development?
• Are there any risk factors present?
• Is the woman in labour?

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Admission CTGs

• Are a poor predictor of fetal compromise during
  labour in low risk women
• There is no current evidence that supports
  routine CTG testing on admission in low risk
  women is therefore not recommended
• Rationale was that this would identify a sub
  group of fetus who would benefit from intensive
  surveillance RCOG
• Make an assessment of the risks to determine
  whether electronic FHR monitoring is required

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Who should have continuous electronic FHR
monitoring?

• Antenatal risk factors
• Prematurity
• Pre-eclampsia/eclampsia
• Diabetes
• Growth restriction
• Non-reassuring antenatal fetal welfare assessment
• Multiple pregnancy
• Malpresentation

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Who should be have continuous electronic FHR
monitoring?

• Intrapartum factors
• Syntocinon
• Meconium
• Epidural
• Suspicious FHR on auscultation
• Prolonged rupture of the membranes
• Prematurity
• Previous C/S

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Practice Recommendations for intermittent
auscultation

• Healthy women with uncomplicated labour IA with
  Pinards/Doppler recommended
• Active labour- after contraction for at least 60
  seconds at least
• every 15mins 1st stage
• every 5mins 2nd stage
• Continuous EFM is recommended if
• Baseline lt 110 or gt160bpm
• Decelerations or intrapartum risk factors develop

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Is the woman established in labour?

• The interpretation of the FHR pattern should be
  considered in context.
• If the woman is not established in labour is
  reactivity present?

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Guidelines

• Education based on Royal College of Obstetrics
  and Gynaecology (RCOG) Guidelines
• The Use of Electronic Fetal Monitoring
• www.rcog.org.uk
• RCOG provide clear descriptions that will provide
  a consistent approach to interpretation

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Lactate of gt 6 pathological
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Categorisation of FHR Features
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Categorisation of FHR Patterns
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Baseline rate

• Normal 110 160bpm
• Bradycardia (moderate) 100 109bpm
• Bradycardia (abnormal) lt 100 bpm
• Tachycardia (moderate) 161 180 bpm
• Tachycardia (abnormal) gt180 bpm
• (RCOG)

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Baseline Rate
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Baseline Bradycardia

• Bradycardia (moderate) 100 109bpm
• Bradycardia (abnormal) lt 100 bpm
• Rare
• Consider the cause if this is a sudden event ?
  prolonged deceleration

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Causes of Baseline Tachycardia

• Excessive fetal movement
• Maternal dehydration
• Prematurity
• Maternal fever
• Maternal or fetal stress causing adrenaline
  release
• Chorioamnionitis

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Tachycardia

• Also seen with fetal asphyxia (low levels of O2)
  particularly in the early stages
• In the presence of true asphyxia, tachycardia is
  most commonly associated with other features such
  as decreased variability

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Variability

• Greater than 5bpm and less than 25bpm
• Increased variability is often seen following an
  acute hypoxic event.
• Should settle after about 10 mins when the fetus
  returns to normal O2 levels

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Saltatory
Saltatory
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Causes of Reduced Variability

• 5bpm fetal sleep or quiet state
• Maternal medications Morphine, Pethidine etc
• Fetal hypoxia depressing the CNS
• Fetal anomalies
• Fetal Cardiac Arrhythmias

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Sinusoidal

• Wave like pattern of 3 5 oscillation / min
  ranging between 5 15 beats

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Accelerations

• Not always present in the intrapartum pattern as
  the most common feature is a deceleration
• A reassuring feature of an intrapartum pattern
• Spontaneous acceleration pH gt7.25

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Decelerations

• Early
• Late
• Variable typical and atypical
• Prolonged

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Early

• Repetitive from one contraction to another
• Recovery to baseline is always at the end on the
  contraction
• Caused by vagal nerve stimulation

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The Fetal Heart Rate Early decelerations

• Begin with head compression during the
  contraction
• This reduction of cerebral blood flow leads to
  hypoxia and hypercapnia
• Hypercapnia leads to hypertension with triggering
  of baroreceptors
• Results in bradycardia mediated by
  parasympathetic nervous system (via the vagal
  nerve)
• Fall in FHR is matched to rise in contraction
  strength
• Not indicative of fetal compromise

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Late Decelerations

• Repetitive from one contraction to the next (3 or
  more)
• Recovery to baseline is late, well after the end
  of the contraction
• More ominous when associated with minimal
  variability ? baseline
• Reflects a change in placental ability to
  adequately meet fetal needs
• May indicate the presence of fetal hypoxia and
  acidosis
• Often signifies fetal decompensation

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The Fetal Heart Rate Late decelerations

• Lates represent fetal hypoxia and are related to
  an interruption in O2 supply at cardiac level
• Reduced O2 leads to stimulation of chemoreceptors
• Results in activation of the cardiac centres in
  the brainstem
• SA node is effected and the FHR slows.
• With the prolonged hypoxia, myocardium is
  effected causing further decrease in the FHR and
  hypotension
• Recovery is slower as the myocardium gradually
  reoxygenates

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Variable Decelerations

• Repetitive or intermittent
• Often mimic letters of the alphabet
• U V W M
• Rapid sudden fall in FHR
• Often rapid recovery
• Reflect some degree of umbilical cord impingement
• Often seen when liquor volume is ?

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Typical Variable - causes

• Compression of blood in umbilical vein results in
  loss of circulating blood volume causing a well
  fetus to have a primary acceleration
  demonstrated by ? autonomic NS activity
  (1stshoulder)
• Followed by partial compression or stretching of
  the umbilical arteries causing blood flow
  interruption and the deceleration.
• This decreases blood flow to the Rt heart causes
  hypotension
• This stimulates the sympathetic nervous system
  and catecholamine release
• Causing a compensatory fetal tachycardia
  following the deceleration (the 2nd shoulder).

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Typical Variable - features?

• A sharp V shaped deceleration caused by
  compression of blood in umbilical arteries
  preceded and followed by an acceleration
  (shoulder)
• The classic typical variable due to a transient
  occlusion of the umbilical cord for such a short
  duration that the period of hypoxia is not enough
  to effect the previously well fetus

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Shoulders

• Baseline Rate

Typical variables
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Atypical Variable Decelerations

• Loss of primary or secondary rise in baseline
  rate (No Shoulders)
• Slow return to baseline FHR after the end of the
  contraction
• Prolonged increase or secondary rise in baseline
  rate (Overshoot)
• Biphasic deceleration (Variable followed by late
  component)
• Loss of variability during a deceleration
• Continuation of the baseline rate at a lower level

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Slow return to baseline

• Concerning feature
• Associated with low Apgar scores and fetal
  hypoxia
• 47 of fetuses will have a one min Apgar score lt
  7 however, only 10 have a five min Apgar lt 7
• Can be improved by inutero resuscitation
• Need to look for other non-reassuring features

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Does not return to baseline
Slow return
Baseline Rate
There is very little time where the FHR returns
to baseline rate
1cm per min
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Slow or no return to baseline
Baseline
1cm per min
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Overshoot
Baseline Rate
1cm per min
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Prolonged Decelerations

• FHR falls for gt 3 minutes
• Usually associated with an acute insult - Top up,
  VE, ? Syntocinon
• FHR pattern before and in recovery indicates
  fetal tolerance - not the deceleration itself
• Should be managed vigorously

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Suspicious FHR Pattern What should you do?

• Maternal
• Position
• Dehydration
• Infection
• Hypotension
• ?V.E/bedpan
• Vomiting/vasovagal
• Analgesia/Drugs

• Mechanical
• Poor quality CTG
• Maternal pulse
• Transducer site
• FSE
• Oxytocics
• Prostaglandins

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Pathological What should I do?

• Roll woman into L) lateral
• Perform Fetal Blood Sampling
• If pH ?7.25 repeat within one hour if the FHR
  abnormality persists
• If pH 7.21-7.24 repeat within 30mins or deliver
  if rapid fall since last FBS
• If pH lt 7.20 DELIVER immediately
• Lactate 4.2 - 4.8 DELIVER.
• All FBS should take into account previous pH,
  rate of progress clinical information

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Abnormal FBS results

• Expedite delivery
• Mother consent
• Urgency should be dictated by severity of FHR
  abnormality maternal factors
• Reasons FBS not appropriate
• maternal or fetal infection
• Fetal bleeding disorders
• Prematurity lt 34 weeks

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Conclusion

• Earlies are caused by vagal nerve stimulation
• Variables are caused by cord compression
• Lates are caused by placental blood flow
• Increasing heart rate and decreased variability
  are non-reassuring and worthy of concern

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References

• RCOG 2001 The Use of Electronic Fetal Monitoring
• www.rcog.org.uk