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Calibration of the CTG

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Calibration of the CTG

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Calibration of the CTG

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Calibration of the CTG

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Features and Terminology of CTG•The four main features of CTG are:

▫Baseline rate.▫Baseline variability.▫Accelerations.▫Decelerations.

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Baseline Fetal Heart Rate•Baseline rate is defined as the level of the fetal

heart rate when it is stable, excluding accelerations and decelerations.

•It is determined over a time of 5-10 minutes, and expressed in beats per minute.Reassuring:Normal baseline 110 – 160

Non-Reassuring:Moderate bradycardiaModerate tachycardia

100 – 109161 – 180

Abnormal:Abnormal bradycardiaAbnormal tachycardia

< 100> 180

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Normal Baseline FHR

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Baseline Bradycardia

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Baseline Tachycardia

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Baseline Variability•Baseline variability is the minor fluctuations in

baseline fetal heart rate occurring over 3-5 cycles/minute.

Reassuring:Normal baseline 5 bpm between contractions

for up to 40 minutesNon-Reassuring:Non-reassuring baseline variability

< 5 bpm for 40 minutes or more, but less than 90 minutes

Abnormal:Abnormal baseline variability

< 5 bpm for 90 minutes or more

Note: if repeated accelerations are present with reduced variability, the CTG should be regarded as reassuring.

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Normal Variability

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Reduced Variability

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Reduced Variability

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Accelerations•Accelerations are abrupt, transient increase

in fetal heart rate of 15 bpm, lasting for 15 seconds.

•The absence of accelerations with an otherwise normal CTG is of uncertain significance.

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Acceleration

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Decelerations•Decelerations are a transient slowing of the

fetal heart rate below the baseline of 15 bpm for 15 seconds.

•There are 5 types of decelerations:▫Early deceleration▫Late deceleration▫Variable deceleration▫Atypical variable deceleration▫Prolonged deceleration

•In addition, there are one specific pattern:▫Sinusoidal pattern

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Early Decelerations• Uniform, repetitive, periodic slowing of the FHR

with onset early in the contraction and return to baseline at the end of contraction.

• The lowest point of the deceleration coincides with the highest point of the contraction wave.

• Usually associated with head compression.• Tend to occur late in the first stage or during the

second stage of labor.

• Benign, not significant, not associated with fetal hypoxia.

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Early Decelerations

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Early Decelerations

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Early Decelerations

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Late Decelerations• Uniform, repetitive, periodic slowing of the FHR

with onset mid- to the end of the contraction.

• The lowest point of the deceleration more than 20 seconds after the peak of the contraction wave, always ending after the contraction.

• In non-accelerative trace, with baseline variability < 5 bpm, the definition would include decelerations < 15 bpm.

• Late decelerations, if present for > 30 minutes, are always indicative of fetal hypoxia, and further action is indicated.

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Late Decelerations

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Late Decelerations

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Late Decelerations

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Variable Decelerations•The MOST COMMON form of decelerations

occurring during labor.

•Variable, intermittent, periodic slowing of the FHR, with rapid onset and recovery.

•Time relationships with contraction waves are variable. Sometimes, they may resemble other types of decelerations in timing and shape.

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Variable Decelerations – cont’d•Variable decelerations are often caused by

umbilical cord compression.

•Variable decelerations are either typical or atypical.

•Typical variable decelerations are an

autonomic nervous system response to cord compression and are indicative of the fetus coping well.

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Variable Decelerations – cont’d•However, the fetus may become tired over time

and, if typical variable decelerations occur with over 50% of contractions for more than 90 minutes, this should be regarded as non-reassuring, particularly if there is any degree of fetal compromise such as fetal growth restriction.

•Atypical variable decelerations may subsequently develop indicating that the fetus is now less able to cope with cord compression.

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Pure (Typical) Variable Decelerations

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Prolonged Decelerations•An abrupt decrease in FHR to levels below

the baseline that lasts at least 60-90 seconds.

•If fetal bradycardia occurs for more than 3 minutes, plan should be made to urgently expedite delivery. A “category 1” birth should be declared and the woman should be immediately transferred to the theatre. If the fetal heart rate recovers within 9 minutes, the decision for immediate delivery should be reconsidered, if reasonable, and in consultation with the woman.

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Prolonged Decelerations

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Sinusoidal Pattern• A regular oscillation of the baseline long-term

variability (resembling a sine wave).

• Smooth, undulating pattern, lasting at least 10 minutes, has a relatively fixed period of 3-5 cycles per minute at an amplitude of 5-15 beats per minute above and below the baseline.

• Baseline variability is absent.

• A true sinusoidal pattern is an abnormal feature and is associated with high rates of fetal morbidity and mortality.

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Sinusoidal Pattern

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Intrapartum CTG Reassuring Non-Reassuring Abnormal

Baseline rate 110 – 160 bpm •100 – 109 bpm•161 – 180 bpm

•< 100 bpm•> 180 bpm•Sinusoidal pattern for 10 min

Comments:

Variability 5 bpm or more < 5 bpm for 40-90 min(in absence of accelerations)

< 5 bpm for 90 minutes (in absence of accelerations)

Comments:

Accelerations present Comments:

Decelerations None •Typical variable decelerations with > 50% of contractions for over 90 minutes•Single prolonged decelerations up to 3 minutes

•Atypical variable decelerations > 50% of contractions for over 30 minutes•Single prolonged deceleration > 3 minutes

Comments:

OpinionNormal CTG(all 4 features reassuring)

Suspicious CTG(one non-reassuring feature)

Pathological CTG(two or more non-reassuring, orone or more abnormal features)

Cervical Dilatation

Cont’s : 10 min

Liquor Color

Gestational Age

Maternal Pulse

Action

Date:Time: Signature: Status: