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.

THANK YOU