interpretation of abnormal ctg pattern_2

8/10/2019 Interpretation of Abnormal CTG Pattern_2

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Interpretation of abnormal CTG

pattern

Ngee Wey Yi & Pariksit Rao


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Categorisation of FHR Features


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Categorisation of FHR Patterns

Normal A CTG where all 4features fall into thereassuring category.

Suspicious A CTG whose features fall into 1of the non-

reassuring categories & the remainder arereassuring.

Pathological A CTG whose features fall into 2 or more non-

reassuring categories or 1or more abnormal

categories.


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Baseline rate

Normal = 110160bpm

Bradycardia (moderate) = 100109bpm

Bradycardia (abnormal) = < 100 bpm

Tachycardia (moderate) = 161180 bpm

Tachycardia (abnormal) = >180 bpm (RCOG)


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Foetal Tachycardia

It can be caused by:

Foetal hypoxia

Chorioamnionitisif maternal fever also present

Foetal or Maternal Anaemia

Foetal tachyarrhythmia

Foetal Bradycardia

Post-date gestation

Occiput posterior or transverse presentations

Prolonged cord compression

Cord prolapse

Epidural & Spinal Anaesthesia

Maternal seizures Rapid foetal descent

If the cause cannot be identified and corrected, immediate delivery isrecommended


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Variability

Refers to the variation of fetal heart rate fromone beat to the next.

Greater than 5bpm and less than 25bpm

Should settle after about 10 mins when the

foetus returns to normal O2 levels

Increased variability is often seen following an

acute hypoxic event.


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To calculate variability you look at how much the peaks & troughs of the

heart rate deviate from the baseline rate (in bpm)

Reassuring 5 bpm

Non-reassuring< 5bpm for between 40-90 minutes Abnormal< 5bpm for >90 minutes

Reduced variability can be caused by:

Foetus sleeping -this should last no longer than 40 minutes most

common cause Foetal acidosis (due to hypoxia)more likely if late decelerations also

present

Foetal tachycardia

Drugsopiates, benzodiazipines, methyldopa, magnesium sulphate

Prematurityvariability is reduced at earlier gestation (


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Acceleration

Accelerations are an abrupt increase in baselineheart rate of >15 bpm for >15 seconds

The presence of accelerations is reassuring

Antenatally there should be at least 2

accelerations every 15 minutes

Accelerations occurring alongside uterine

contractions is a sign of a healthy foetusHowever the absence of accelerations with an

otherwise normal CTG is of uncertain significance


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Deceleration

Decelerations are an abrupt decrease in baselineheart rate of >15 bpm for >15 seconds.

4 types: Early

LateVariabletypical and atypical

Prolonged


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Early deceleration

Early decelerations start when uterine contraction begins & recover

when uterine contraction stops.

This is due to increased foetal intracranial pressure causing increased

vagal tone.

It therefore quickly resolves once the uterine contraction ends &

intracranial pressure reduces.

This type of deceleration is therefore considered to be physiological &

not pathological.


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Late deceleration

Begin at the peak of uterine contraction & recover after

The contraction ends.

Indicates there is insufficient blood flow through the uterus & placentacausing foetal hypoxia & acidosis

The presence of late decelerations is taken seriously & foetal blood sampling

for pH is indicated. If foetal blood pH is acidotic it indicates significant foetal

hypoxia & the need for emergency C-section


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Variable deceleration

2 types: Typical

Atypical

Repetitive or intermittent Often mimic letters of the alphabet

U V W M

Reflect some degree of umbilical cord impingement

Often seen when liquor volume is

Prolonged Decelerations

FHR falls for > 3 minutes

If it lasts between 2-3 minutes it is classed as Non-Reasurring

If it lasts longer than 3 minutes it is immediately classed as Abnormal Action must be taken quicklye.g. Foetal blood sampling / emergency

C-section


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SinusoidalVery rare pattern

Sign of a dying baby

No beat to beat variability

A sinusoidal pattern indicates:

Severe foetal hypoxia

Severe foetal anaemiaFoetal/Maternal Haemorrhage

Immediate C-section is indicated for this kind of pattern.

interpretation of abnormal ctg pattern_2

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