What is cardiotocography (CTG)?
Cardiotocography (CTG) or electronic foetal monitoring (EFM) is a medical test that monitors your baby's heart rate and your uterine contractions during pregnancy and labour. This noninvasive, external electronic monitoring helps your healthcare providers assess your baby's well-being and detect any signs of distress before birth and throughout the labour process.
The cardiotocograph device uses external sensors placed on your abdomen to continuously track both your foetal heartbeat pattern and the strength and frequency of your contractions, providing information about how your baby is responding to the labour process.
When is a CTG needed?
CTG is typically used during your last trimester of pregnancy (from 29 to 40 weeks) to assess your baby's wellbeing. Your healthcare provider may recommend CTG monitoring in the following situations:
Your baby moves slower than usual or shows irregular movement patterns.
Your baby appears smaller than expected or isn't growing properly.
Your healthcare provider suspects reduced blood flow from your placenta to your baby.
You have either too much or too little amniotic fluid around your baby.
You are carrying multiple babies (such as twins or triplets).
You have medical conditions during pregnancy that require extra monitoring, such as:
Gestational hypertension
Diabetes mellitus
High blood pressure
You are past your due date.
You have experienced a previous baby loss in the second half of pregnancy.
As part of monitoring during labour and delivery.
Other high-risk pregnancy situations where your healthcare provider determines additional monitoring would be beneficial.
For more information about CTG monitoring and whether it’s suitable for your pregnancy, consider speaking with a healthcare professional. You may contact Thomson Medical to arrange a consultation for personalised guidance tailored to your individual pregnancy care needs.
How does CTG work?
Depending on your situation, CTG may use one of two forms of monitoring methods:
External CTG monitoring
An external CTG uses a special type of ultrasound, called Doppler ultrasound, to monitor your baby's heart rate. This ultrasound technology uses high-frequency sound waves that you cannot hear but can be detected by the monitoring equipment to measure moving structures like your baby's heartbeat.
Here’s what you can expect during the external monitoring:
Two sensors are placed on your abdomen and secured with elastic belts.
One sensor uses Doppler ultrasound to detect your baby's heart rate.
The other sensor measures how tense your abdomen becomes to show when your uterus is contracting.
The monitoring is completely non-invasive and safe for both you and your baby.
Internal CTG monitoring
If your healthcare provider cannot get a good reading of the baby’s heartbeat using an external CTG during labour, they may recommend internal monitoring. This method uses a small device called an electrode, that’ll be inserted through the vagina and neck of the womb and gently attached to your baby's scalp.
Both types of monitoring work continuously to provide your healthcare team with real-time information about how your baby is responding during pregnancy or labour.
What can CTG show?
CTG monitoring provides your healthcare team with important information about your baby's condition. It can detect when your baby is distressed during labour, which is often caused by not receiving enough oxygen. The CTG tracks several key indicators:
Your baby's heart rate
Your baby's normal heart rate should be between 110 and 160 beats per minute. If your baby's heart rate is higher or lower than this normal range, it may indicate a problem that requires your healthcare provider's attention.
Heart rate variability
Normal variability in your baby's heart rate is a positive sign that indicates your baby's brain is functioning well. This means there should be slight changes in heart rate from beat to beat. If your baby's heart rate stays very similar for extended periods without these normal fluctuations, the result could suggest a concern that needs further assessment.
Heart rate patterns in response to contractions
Your healthcare team will look for two main types of heart rate changes during contractions:
Accelerations
These occur when your baby's heart rate increases briefly during a contraction and then returns to normal. This is typically a reassuring sign that your baby is responding well.
Decelerations
These happen when your baby's heart rate decreases temporarily. This can be normal if it occurs at the beginning of a contraction and returns to normal immediately after the contraction ends. However, decelerations may be concerning if it:
Happen without contractions
Occur late in a contraction
Last for a long time after the contraction finishes
These patterns may indicate that your baby is experiencing difficulty.
How to read a CTG?
Your healthcare professionals will use the information provided above to categorise your CTG results, as follows:
Reassuring:
No signs of problems with your baby – everything appears normal.
Suspicious:
Certain signs may indicate that your baby is experiencing mild distress and requires closer monitoring.
Pathological:
Signs that strongly suggest your baby is in distress and may require immediate intervention.
If your results are suspicious or pathological, your healthcare team will assess the situation further and try to address anything that might be affecting your baby. If these measures don't improve the situation, or if the CTG indicates your baby is in serious distress, they may recommend immediate delivery to ensure your baby's safety.
Are there any side effects or complications from cardiotocography?
The CTG monitoring technique is generally very safe for both you and your baby since it doesn't use any radiation. However, there are a few considerations to keep in mind:
External CTG monitoring
The main limitation you might experience with external CTG is restricted mobility. The monitoring belts around your abdomen may limit your ability to move around freely during the foetal heart rate monitoring.
Your healthcare team can help you find comfortable positions and may be able to adjust the monitoring setup to allow for some movement when possible.
Internal CTG monitoring considerations
Internal CTG monitoring may not be suitable for everyone. If you have certain infections, such as hepatitis B, hepatitis C, or HIV, your healthcare provider will typically avoid internal monitoring due to the risk of transmitting them to your baby during the procedure.
FAQ
What does a CTG scan show?
Your CTG scan shows your baby's heart rate patterns and your uterine contractions during pregnancy and labour. This continuous monitoring during pregnancy helps your healthcare team assess how your baby is responding to the pregnancy and labour processes.
What is a normal CTG for a baby?
A normal CTG result for your baby during labour includes the following:
Baseline heart rate:
Between 110 and 160 beats per minute
Normal variability:
Greater than 5 beats per minute, showing healthy fluctuations in heart rate
Absence of variable decelerations:
No worrying drops in heart rate
Accelerations:
Brief increases in heart rate (these may or may not be present, but are reassuring when they occur)
Your healthcare provider will interpret these patterns together to determine if your baby's CTG is reassuring.
What is the purpose of conducting a CTG test during pregnancy?
CTG is used to assess foetal well-being, detect possible signs of foetal distress, and monitor how your baby responds to the stress of labour and contractions. It is a key part of monitoring techniques for a healthy pregnancy.
In what month is CTG done?
CTG is usually performed during your last trimester of pregnancy, from 29 to 40 weeks (which corresponds to your 7th, 8th, or 9th month of pregnancy). Your healthcare provider will determine the specific timing based on your individual pregnancy needs.
What is the difference between a CTG and an ECG?
A CTG is a medical device that uses ultrasound to detect a baby's heart rate and a mother's uterine contractions during pregnancy and labour, while an electrocardiogram (ECG) is a medical test that is used to analyse the electrical activity of your heart.
Can CTG detect baby movements?
Yes, CTG is able to detect a baby's movement. It uses sensors to primarily focus on the baby’s heart rate and mother’s uterine contraction along with the baby's movement.
What is foetal distress?
Foetal distress refers to signs that your baby may not be getting enough oxygen or may be experiencing other complications during pregnancy or labour. Your healthcare medical team identifies this through changes in heart rate patterns, reduced foetal movement, or other concerning signs detected through foetal monitoring.
What causes foetal distress?
There are many different reasons why your baby may become distressed during pregnancy or labour. Your baby may be at higher risk of distress if:
Placental complications:
Health complications that can affect how much blood, oxygen, and nutrients reach your baby through the placenta.
Multiple pregnancy:
If you're expecting twins or more, one or both of your babies are more likely to experience distress.
Growth concerns:
If your baby is smaller than expected for their gestational age, they may be more prone to distress.
Maternal age:
If you're 35 years or older, there may be increased risk factors.
Post-term pregnancy:
If you're overdue (past your due date).
The information provided is intended for general guidance only and should not be considered medical advice. For personalised recommendations based on your medical conditions, request an appointment with Thomson Medical.
For more information, contact us:
Thomson Specialists (Women's Health)
Thomson Women's Clinic (TWC)
Request an Appointment