Intrapartum fetal monitoring for undergraduate

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INTRAPARTUM FETAL MONITORING

• DR MANAL BEHERY
• Zagazig University, EGYPT

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The three unique risk factors for fetus during
labor

• Factor of uterine contraction
• Factor of cord accident
• Factor of head compression

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Factor of uterine contraction

• Let us see what happen to oxygenation and blood
  supply of the fetal brain during a uterine
  contraction?

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• De-oxy-Hb 0.79micromol/100Gm of brain
• Oxy Hb 0.19 micromol/100Gm of brain
• CerebralO2 saturation 9
• Cerebral blood volume 0.33 ml/100Gm of
• In spite of this slightly worrying picture,
• Nothing harmful effect happen if
• fetus is healthy
• labor contraction are normal
• Placenta has adequate reserve

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Fetal distress, birth asphxia are likely to
occur if

• The fetus is already compromised
  antenatally---even with normal uterine
  contraction
• The uterine contraction are exaggerated------even
  with healthy fetus and adequate placental reserve

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Factor of cord accident

• Only during labor cord prolapse ,presentation
  and entanglements become apparent either by
  compression or stretch secondary to uterine
  contraction

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Factor of head compression

• Some degree of compression is inevitable during
  normal labor But
• Excessive compression over long period causing
  supermoulding
• as in obstructed labor
• may cause fetal hypoxia

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Methods available for fetal monitering in
labor

• Intermittent auscultation
• CTG Fetal electrocardiography
• Scalp stimulation
• Vibroacoustic stimulation
• Fetal scalp sampling ? PH determination
• Fetal pulse oximetry

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Important definations

• Hypoxia Decreased po2 level in tissues.
• Hypoxima Decreased po2 level in blood.
• Acidosis Decreased PH in tissues.
• Acidemia Decreased PH in blood.
• Ashyxia Hypoxia with metabolic acidosis.

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Aim of intrapertum fetal monitering

• 1- to detect the earliest stages of hypoxia or
  even (hypoxic acidemia ) so therapy can be
  directed to prevent asphyxia and asphyxial
  damage( e.g Cerebral palsy)
• 2-To Improve perinatal morbidity mortality

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What is Cardiotocography(CTG)?

• It is a paper record of the continuous FHR
  blotted simultaneously with a record of uterine
  activity
• Ultrasound (cardio)
• transducer
• Tocotransducer

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External monitoring

• Doppler ultrasound transducer
• FHR
• Tocotransducer(contraction)

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Internal monitoring
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What is Admission test ?

• Ideally every fetus every fetus should be
  screened by CTG for a short period (20 min) right
  on admission in labor.
• From nature of the trace determine
• Intensity of monitoring Whether the case should
  be monitored clinically or by CTG
• Duration and frequency of monitoring Whether the
  case should be covered by CTG continuously or
  intermittently

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Interpreting FHR trace

• 4 components
• Base line FHR
• Baseline variability
• Accelerations
• Decelerations

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Baseline FHR

• The dominant reading taken 10 min
• Normal baseline FHR 110-160(pbm)
• Controlled by
• atrial
• pacemaker

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Tachycardia FHRgt160 bpm
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Baseline bradycardia FHRlt110bpm
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Baseline varibility

• The Oscaltatory pattern of FHR when recorded on a
  graph.
• Short term(beat t0 beat)
• is the fluctuation of HR over short interval
• Long term
• is the fluctuation over long interval(2 min)
• Indicates mature fetal neurologic system

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Baseline varibility

• Short term variability
• (scalp electrode)
• Long term variability
• defined as 3-5 cycle/min

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Baseline varibility
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No variability (0-2 ?????/????)
No variability (0-2 ?????/????)
Minimal variability (3-4 ?????/????)
Moderate variability (11-25 ?????/????)
Moderate variability (11-25 ?????/????)
Mark variability (gt25 ?????/????)
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Changes in fetal HR

• Peroidic changes Occur with contraction
• Episodic changes (non peroidic)do not occur with
  contraction

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Accelaration

• Increase in FHR with contraction or with other
  activities
• Can be periodic or episodic
• Increase15pbm
• lasting 15 sec
• Return to base line lt2 min

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Accelaration
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Decelerations Decelerations

• Transient slowing of
• FHR below the
• baseline level
• more than 15 bpm
• and lasting for 15 sec.
• or more.

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Early Decelerations

• Uniform
• Synchronous with contraction (mirror image)
• Rarely fall below 110 (pbm)
• Due to head compression
• Should not be disregarded
• if they appear early in labor or Antenatal.

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Early Decelerations
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Late Deceleration

• Uniform
• Start after peak of contraction
• Associated with decreased
• Variability
• Reflect a baroreceptor
• response
• Indicate fetal hypoxia

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Late Deceleration
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Repetitive late decelration

• increases risk of
• Umbilical artery acidosis
• Apgar score lt 7 at 5 ms
• Cerebral palsy
• If associated with
• decrease or loss of
• variability

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Variable Deceleration (the most common type)

• Varible in appearance and Timing.
• May be assoicated with
• increased variability .
• Reflect umbilical cord compres
• Observed in up to 50 of NSTs compression
• Of no clinical significance
• if non recurrent
• .

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Variable Deceleration
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Prolonged Deceleration deceleration

• A deceleration that lasts more than 90
• seconds (but less than 10 minutes)
• Drop in FHR of 30 bpm or More
• Reduction in O2 transfer to placenta.
• Associated with poor neonatal outcome

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Prolonged Deceleration
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Sinusoidal pattern

• Regular Oscillation of the Baseline long-term
  Variability resembling a Sine wave ,with no beat
  to -beat Variability.
• Has fixed cycle of 3-5 pbm with amplitude of
  5-15 bpm and above but not below the baseline.
• Should be viewed with suspicion as poor
  outcome has been seen (eg Feto-maternal
  haemorrhage)

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Sinusoidal pattern
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What are the features of a normal tracing?

• Baseline FHR 110-160 BPM
• Baseline Variability gt 5 pbm (10-25)
• 2 Accelerations gt 15 BPM gt 15 sec / 20 min trace
• No decelrations

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Normal -Reassuring CTG
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Interpertation of CTG

• Normal -Reassuring(R)- CTG with all 4
  Features
• Suspicious (equivocal)- one non reassuring
  category and reminder are reassuring
• Abnormsal -Non reasurring (NR) - 2 or more
  non-reassuring categories or one or more abnormal
  categories.

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Interpertation of CTG
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Is Normal CTGs always Reassuring?

• With normal CTC the chance of fetus to develop
  hypoxia is 1.5 due to unpredictable acute events
  
• So a normal CTG is always Reassuring

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Is NR CTGs always worrisome ?

• 60 CTG in Labour have 1 abnormal feature
• Only 15-20 of NR CTGs are pathological.
• High false positive rate with unnecessary
  operative intervention for fetal distress.
• Thus NR CTG is not always worrisome.

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?? To reduce CS.
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Consider these factors with abnormal CTG

• Clinical indication of doing CTG
• Abnormal patch of tracing from high risk case
  differ that from no risk case
• Maturity of the fetus
• Reduced variability and baseline tachycardia is
  conmen in preterm
• State of maternal pulse
• Drugs may cause maternal and fetal tachycaedia
• Check blood pressure for hypotension in patients
  on epidural.

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Consider these factors with abnormal CTG
In case of abnormal trace consider these fectots

• Posture of patient during CTG
• Supine position give abnormal tracing
• Some cord compression can get released by
  change posture and must be tried with variable
  deceleration
• Congenital fetal malformation
• Color Doppler of fetal heart to exclude
  congenital heart block
• Stage of labor and expected time of delivery
  Wether to deliver immediate or give sometime
  under close observation

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Suspicious (Equivocal)CTG

• Do continuous monitoring for further development
  towards better or worse trace while instituting
  the corrective measures.
• Ideally check condition of fetus by FAS or FBS or
  scalp stimulation test.
• However ,if liquor is meconium stained ---Deliver
  immediately

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Correct reversible causes

• Change mother position from supine to left
  lateral position-----increase uterine blood flow
• Improve maternal oxygenation100 O2 by masK
• Correct maternal hypotension IV fluid
• Decrease or stop any oxytocin infusion
• Remove vaginal prostaglandins

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Secondary tests of fetal well-being

• Vibro-acoustic stimulation
• Used as a substitute for scalp sampling when CTG
  is NR
• Normal ----------if FHR acceleration gt 15 bpm
  for 15 seconds within 15 seconds after the
  stimulation with prolonged fetal movements.
• Abnormal ----Only 50 have acidotic PH

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Fetal blood sampling

• If the pH gt7.25 --- observe.
• If the pH 7.2 and 7.25---repeated
• within 30 minutes.
• If the pH lt7.2----repeat immediately
• If pH still low -- Prompt delivery

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• Scalp stimulation.
• Firm digital pressure
• Gentile pinch by atramatic Allis forceps
• Fetal pulse oximetry.

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