INTRAPARTUM FETAL MONITORING DR MANAL BEHERY Zagazig University, EGYPT
The three unique risk factors for fetus during laborFactor of uterine contractionFactor of cord accidentFactor 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 healthy labor contraction are normal Placenta 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 supermouldingas 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) transducer Tocotransducer
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”
Interpreting FHR trace 4 components Base line FHR Baseline variability Accelerations Decelerations
Baseline FHR The dominant reading taken ≥10 min Normal baseline FHR 110-160(pbm) Controlled byatrialpacemaker
Tachycardia FHR>160 bpm
Baseline bradycardia FHR<110bpm
Baseline varibilityThe Oscaltatory pattern of FHR when recorded on a graph.Short term(beat t0 beat) is the fluctuation of HR over short intervalLong term is the fluctuation over long interval(≥2 min)Indicates mature fetal neurologic system
Baseline varibility Short term variability(scalp electrode) Long term variability defined as 3-5 cycle/min
Changes in fetal HRPeroidic changes: Occur with contractionEpisodic changes (non peroidic):do not occur with contraction
Accelaration Increase in FHR with contraction or with other activities Can be periodic or episodic Increase15pbm lasting 15 sec Return to base line <2 min
Decelerations DecelerationsTransient slowing ofFHR below thebaseline levelmore than 15 bpmand 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 disregardedif they appear early in labor or Antenatal.
Late Deceleration Uniform Start after peak of contraction Associated with decreasedVariability Reflect a baroreceptorresponse Indicate fetal hypoxia
Repetitive late decelrationincreases risk of Umbilical artery acidosis Apgar score < 7 at 5 ms Cerebral palsy If associated withdecrease or loss of variability
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.
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
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)
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 featureOnly 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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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 pulseDrugs may cause maternal tachycardia– fetal tachycaedia Check blood pressure for hypotension in patients on Epidural
Consider these factors with abnormal CTG Posture of patient during CTGo Supine position give abnormal tracingo Some cord compression can get released by change posture and must be tried with variable deceleration Congenital fetal malformationColor 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 masKCorrect 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---repeatedwithin 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.