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.
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.
