Download - Updated intrapartum fetal monitoring
INTRAPARTUM FETAL MONITORING
DR MANAL BEHERYZagazig University, EGYPT
The three unique risk factors for fetus during labor
Factor of uterine contraction
Factor of cord accident
Factor of head compression
Factor of uterine contraction
Let us see what happen to oxygenation and blood supply of the fetal brain during a uterine contraction?
De-oxy-Hb 0.79micromol/100Gm of brain
Oxy –Hb 0.19 0.79micromol/100Gm of brain
CerebralO2 saturation 9% Cerebral blood volume 0.33 ml/100Gm
ofIn spite of this slightly worrying picture,Nothing harmful effect happen if fetus is healthylabor contraction are normalPlacenta has adequate reserve
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
Factor of cord accident
Only during labor cord prolaps ,presentation and entanglements (occult or overt) become apparent either by compression or stretch secondary to uterine contraction
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
Methods available for fetal monitering in labor
Intermittent auscultation
CTG Fetal electrocardiography Scalp stimulation
Vibroacoustic stimulation
Fetal scalp sampling PH determination
Fetal pulse oximetry
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 acidosis.
Aim of intrapertum fetal monitering
1- to detect the earliest stages of hypoxia or (hypoxic acidemia ) so therapy can be directed to prevent asphyxia and asphyxial damage
2-To Improve perinatal morbidity & mortality
What is Cardiotocography(CTG)?
It is a paper record of the continuous FHR blotted simultaneously with a record of uterine activity
Ultrasound (cardio) transducerTocotransducer
External monitoring
Doppler ultrasound transducer FHR
Tocotransducer(contraction)
Internal monitoring
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 determineIntensity 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”
Interpreting FHR trace
4 components
Base line FHR
Baseline variability
Accelerations
Decelerations
Baseline FHR
The dominant reading taken ≥10 minNormal baseline FHR 110-160(pbm)
Controlled byatrial pacemaker
Tachycardia FHR>160 bpm
Baseline bradycardia FHR<110bpm
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
Baseline varibility
Short term variability (scalp electrode)
Long term variabilitydefined as 3-5 cycle/min
Baseline varibility
No variability (0-2 ครั้��ง/นาที)
Mark variability (>25 ครั้��ง/นาที)
Moderate variability (11-25 ครั้��ง/นาที)
No variability (0-2 ครั้��ง/นาที)
Moderate variability (11-25 ครั้��ง/นาที)
Minimal variability (3-4 ครั้��ง/นาที)
Changes in fetal HR
Peroidic changes: Occur with contraction
Episodic changes (non peroidic):do not occur with contraction
Accelaration
Increase in FHR with contraction or with other activities
Can be periodic or episodicIncrease15pbm lasting 15 sec Return to base line <2 min
Accelaration
Decelerations Decelerations
Transient slowing of FHR below the baseline levelmore than 15 bpm
and lasting for 15 sec. or more.
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.
Early Decelerations
Late Deceleration
UniformStart after peak of contractionAssociated with decreased VariabilityReflect a baroreceptor responseIndicate fetal hypoxia
Late Deceleration
Repetitive late decelration
increases risk ofUmbilical artery acidosis
Apgar score < 7 at 5 ms
Cerebral palsy If associated with
decrease or loss ofvariability
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
.
Variable Deceleration
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
Prolonged Deceleration
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)
Sinusoidal pattern
What are the features of a normal tracing?
Baseline FHR 110-160 BPM
Baseline Variability > 5 pbm (10-25)
2 Accelerations > 15 BPM > 15 sec / 20 min trace
No decelrations
Normal -Reassuring CTG
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.
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
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.
?? To reduce CS….
Consider these factors with abnormal CTG
Clinical indication of doing CTG Abnormal patch of tracing from high risk case
differ that from no risk caseMaturity of the fetus Reduced variability and baseline tachycardia
is conmen in preterm State of maternal pulseDrugs may cause maternal tachycardia– fetal
tachycaediaCheck blood pressure for hypotension in
patients on Epidural
Consider these factors with abnormal CTG
Posture of patient during CTGo Supine position give abnormal tracing o 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 blockStage of labor and expected time of delivery Wether to deliver immediate or give sometime under close observation
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
Correct reversible causes
Change mother position from supine to left lateral position-----increase uterine blood flow
Improve maternal oxygenation—100% O2 by masK
Correct maternal hypotension –IV fluid
Decrease or stop any oxytocin infusion
Remove vaginal prostaglandins
Secondary tests of fetal well-being
Vibro-acoustic stimulation
Used as a substitute for scalp sampling when CTG –is NR
Normal ----------if FHR acceleration > 15 bpm for 15 seconds within 15 seconds after the stimulation with prolonged fetal movements.
Abnormal ----Only 50% have acidotic PH
Fetal blood sampling
If the pH >7.25 --- observe. If the pH 7.2 and 7.25---repeated within 30 minutes.
If the pH <7.2----repeat immediately
If pH still low -- Prompt delivery
Scalp stimulation. Firm digital pressure
Gentile pinch by atramatic Allis forceps
Fetal pulse oximetry.
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