Cardiotocography (CTG)

Question 1

Remember DR C BRAVADO

Answer 1

• D - Define risk
• C - Contractions
• BRa - Baseline rate
• V - Variability
• A - Accelerations
• D - Decelerations
• O - Overall impression

Question 2

Define risk

Answer 2

• High risk features include:
  
  • Maternal medical illness
    
    • Gestational diabetes
    • Hypertension
    • Asthma
  • Obstetric complications
    
    • Multiple gestation
    • Post-date gestation
    • Previous cesarean section
    • Intrauterine growth restriction
    • Premature rupture of membranes
    • Congenital malformations
    • Oxytocin induction/augmentation of labour
    • Pre-eclampsia
  • Other risk factors
    
    • Absence of prenatal care
    • Smoking
    • Drug abuse

Question 3

Contractions

Answer 3

• Number in a 10 minute period (each big square is 1 minute)
  
  • Ideally 3-4 in active labour
• Duration - how long do they last?
• Intensity - asessed using palpation

Question 4

Baseline rate of the fetal heart

Answer 4

• Average rate
• Normal between 110-160bpm
• Fetal tachycardia caused by:
  
  • Fetal hypoxia
  • Chorioamnionitis – if maternal fever also present
  • Hyperthyroidism
  • Fetal or maternal anaemia
  • Fetal tachyarrhythmia
• Fetal bradycardia caused by:
  
  • Prolonged cord compression
  • Cord prolapse
  • Epidural and spinal anaesthesia
  • Maternal seizures
  • Rapid fetal descent

NB - Feta bradycardia between 100-120 can be normal in postdate gestation and occiput posterior or transverse presentations.

Question 5

Variability

Answer 5

• 5-25bmp reassuring
• Abnormal if:
  
  • Less than 5bpm for between 30-50 minutes
  • More than 25bpm for 15-25 minutes
• Reduced variability seen in:
  
  • Fetal sleeping – this should last no longer than 40 minutes (most common cause)
  • Fetal acidosis (due to hypoxia) – more likely if late decelerations are also present
  • Fetal tachycardia
  • Drugs – opiates / benzodiazepines / methyldopa / magnesium sulphate
  • Prematurity – variability is reduced at earlier gestation (<28 weeks)
  • Congenital heart abnormalities

Question 6

Accelerations

Answer 6

• Increase in baseline fetal HR >15bpm for >15 seconds

Question 7

Decelerations

Answer 7

• Decrease in fetal HR >15bpm for >15 seconds
• Early decelerations start when uterine contraction begins and recover when uterine contraction stops - due to increased fetal intracranial pressure causing increased vagal tone - if quickly resolves once uterine contraction ends then physiological and not pathological
• Variable decelerations are decelerations with a variable recovery phase - usually caused by umbilical cord compression and fetus is not yet hypoxic but has reduced blood flow - can sometimes be resolved if mother changes position
• Late decelerations caused by maternal hypotension, pre-eclampsia and uterine hyperstimulation
• Prolonged decelerations (>2-3 minutes)
• Sinusoidal pattern is rare and very concerning as it indicates severe fetal hypoxia, severe fetal anaemia or fetal/maternal haemorrhage

Question 8

Overall impression

Answer 8

• Reassuring
• Suspicious
• Abnormal