Baseline Rate of the Fetal Heart
The baseline rate is the average heart rate of the fetus within a 10-minute window.
Look at the CTG and assess what the average heart rate has been over the last 10 minutes, ignoring any accelerations or decelerations.
A normal fetal heart rate is between 110-160 bpm.
Fetal tachycardia
Fetal tachycardia is defined as a baseline heart rate greater than 160 bpm.
Causes of fetal tachycardia include:
Fetal hypoxia
Chorioamnionitis
Hyperthyroidism
Fetal or maternal anaemia
Fetal tachyarrhythmia
Fetal bradycardia
Fetal bradycardia is defined as a baseline heart rate of less than 100 bpm.
It is common to have a baseline heart rate of between 100-120 bpm in the following situations:
Postdate gestation
Occiput posterior or transverse presentations
Severe prolonged bradycardia (less than 80 bpm for more than 3 minutes) indicates severe hypoxia.
Causes of prolonged severe bradycardia include:
Prolonged cord compression
Cord prolapse
Epidural and spinal anaesthesia
Maternal seizures
Rapid fetal descent