Cardiotocography Flashcards
What is CTG used for
Measure the fetal heart rate and the contractions of the uterus
How is CTG done
Two transducers are placed on the abdomen to get the CTG readout:
- One above the fetal heart to monitor the fetal heartbeat
- One near the fundus of the uterus to monitor the uterine contractions
How does CTG work
The transducer above the fetal heart monitors the heartbeat using Doppler ultrasound.
The transducer above the fundus uses ultrasound to assess the tension in the uterine wall, indicating uterine contraction.
Indications for Continuous CTG Monitoring
Sepsis Maternal tachycardia (> 120) Significant meconium Pre-eclampsia (particularly blood pressure > 160 / 110) Fresh antepartum haemorrhage Delay in labour Use of oxytocin Disproportionate maternal pain
Key features to look for on CTG
Contractions – the number of uterine contractions per 10 minutes
Baseline rate – the baseline fetal heart rate
Variability – how the fetal heart rate varies up and down around the baseline
Accelerations – periods where the fetal heart rate spikes
Decelerations – periods where the fetal heart rate drops
What do contractions show
Activity of labour.
Too few contractions - labour is not progressing.
Too many contractions - uterine hyperstimulation
Baseline rate
Reassuring - 110 - 160
Non reassuring - 100 - 109 or 161 - 180
Abnormal - < 100 or > 180
Variability
Reassuring - 5 - 25
Non reassuring:
- Less than 5 for 30 – 50 minutes or
- More than 25 for 15 – 25 minutes
Abnormal:
- Less than 5 for over 50 minutes or
- More than 25 for over 25 minutes
Decelerations
Fetal HR drops in response to hypoxia to conserve oxygen.
Types of deceleration
There are four types of decelerations to be aware of:
Early decelerations
Late decelerations
Variable decelerations
Prolonged decelerations
Early decelerations
Gradual dips and recoveries in heart rate that correspond with uterine contractions.
The lowest point of the declaration corresponds to the peak of the contraction.
Normal and not considered pathological - caused by the uterus compressing the head the fetus, stimulating the vagus nerve of the fetus, slowing the heart rate
Late decelerations
Gradual falls in heart rate that starts after the uterine contraction has already begun.
There is a delay between the uterine contraction and the deceleration.
The lowest point of the declaration occurs after the peak of the contraction.
Caused by hypoxia in the fetus - more concerning finding.
What can cause late decelerations
Excessive uterine contractions
Maternal hypotension
Maternal hypoxia
Variable decelerations
Abrupt decelerations that may be unrelated to uterine contractions.
Fall of more than 15 bpm from the baseline
The lowest point of the declaration occurs within 30 seconds, and the deceleration lasts less than 2 minutes in total.
Often indicate intermittent compression of the umbilical cord, causing fetal hypoxia
Brief accelerations before and after the deceleration are known as shoulders, and are a reassuring sign that the fetus is coping
Reassuring CTG
No decelerations, early decelerations or less than 90 minutes of variable decelerations with no concerning features.
Non-reassuring or abnormal
Regular variable decelerations and late decelerations
Suspicious CTG
Single non-reassuring feature
Pathological CTG
2 non-reassuring features or a single abnormal feature
Need for urgent intervention
Acute bradycardia or prolonged deceleration of more than 3 minutes
Management of an abnormal CTG
Escalating to a senior midwife and obstetrician
Further assessment for possible causes, such as uterine hyperstimulation, maternal hypotension and cord prolapse
Conservative interventions - repositioning the mother or giving IV fluids for hypotension
Fetal scalp stimulation (an acceleration in response to stimulation is a reassuring sign)
Fetal scalp blood sampling to test for fetal acidosis
Delivery of the baby (e.g. instrumental delivery or emergency caesarean section)
Fetal Bradycardia
3 minutes – call for help
6 minutes – move to theatre
9 minutes – prepare for delivery
12 minutes – deliver the baby (by 15 minutes)
Sinusoidal CTG
Can indicate severe fetal compromise
Gives a pattern similar to a sine wave, with smooth regular waves up and down that have an amplitude of 5 – 15 bpm.
Associated with severe fetal anaemia -
caused by vasa praevia with fetal haemorrhage
DR C BRaVADO
DR – Define Risk (define the risk based on the individual woman and pregnancy before assessing the CTG)
C – Contractions
BRa – Baseline Rate
V – Variability
A – Accelerations
D – Decelerations
O – Overall impression (given an overall impression of the CTG and clinical picture)
