CTG Interpretation

Written by: Anli Yue Zhou from Manchester University,

Indications

 

Cardiotocograms (CTG's), are performed for a number of reasons. They can be done continuously if the mother is defined as high risk, otherwise they are done every 15 minutes in the first stage of labour, and every 5 minutes in the second stage.

 

Indications for CTG

Interpretation

 

Use the DR C BRAVADO method

 

1. Demographics of the patient

2. indication of CTG

3. Any obvious abnormalities

 

DR - Define Risk  -? Pre-eclampsia, diabetes, IUGR, smoker etc

C - Contractions -  in the 2nd stage of labour - ideally <5 contractions in 10 minutes

BRA - Baseline rate  110-160bpm

V - Variability 5-25 beats

A - Accelerations - 2 in 20 minutes

D - Decelerations  - abnormal

O - Overall risk:

 

• Normal

• Suspicious - <110 OR >160bpm, reduced variability, <90 minutes of uncomplicated early or variable deceleration.

- Re-do the CTG and reassess in one hour

• Abnormal - Immediate management to deliver baby

 - if the head is engaged- usually instrumental delivery

 - if the head is not engaged- emergency caesarean section

 

A 'normal' CTG trace

Abnormalities

1. Flat trace (reduced variability)

• Sleep phase of baby

• Depressants e.g opiates

• Thumb sucking

• Maternal dehydration

 

2. Early deceleration

Occurs at the beginning of uterine contractions

Heart rate returns to baseline rate by the end of contractions

Usually decelerates <40bpm

Most commonly due to head compression causing vagal nerve stimulation, hence the temporary reduction in heart rate

Can also be due to cord compression or fetal hypoxia

 

3. Variable deceleration

Occurs at variable time during contraction

Has irregular shape usually >50bpm deceleration

*usually an indication for fetal blood sampling- if <7.2 then baby is delivered immediately

Due to cord compression

 

4. Late deceleration

Deceleration trough is past the peak of the contraction

- associated with Fetal hypoxia

 

Prognosis

 

The CTG is felt to have a poor prognosis if the following are present:

 

• Loss of variability

• Fetal tachycardia>160bpm

• Late deceleration

 

This usually indicates fetal hypoxia.