A Cardio Toco graph or CTG monitors the relationship between baby’s heart rate and the contractions of the uterus.
- The upper line represents the baby’s heart rate
- The bottom line records the contractions – these readings can be affected by the positioning of the belt and how tight it is.
- Contractions: up to 5 in 10min
- Baseline: Normally between 110 – 160bpm (beats per minute) determined over a period of 10min
- Beat to beat variability: the variation in baby’s heart rate, normal 5 -15bpm
- Accelerations: 15bpm from baseline is reassuring in labour but not necessary.
- Decelerations: 15bpm from baseline is normal in 2nd stage during pushing and is caused by pressure of baby’s head moving down the birth canal.
- Beat to beat variability: undetectable from baseline (absent) considered pathological.
- Beat to beat variability: below 5bpm (minimal) considered suspicious.
|Antenatal (no regular contractions)||In Labour|
|Reassuring:||All features normal||Normal:||All features normal|
|Non reassuring:||One feature abnormal||Suspicious:||One feature abnormal|
|Abnormal:||Two or more features abnormal||Pathological:||Two or more features abnormal|
Mind and severe variable decelerations:
– Prolonged deceleration:
- The woman should be assisted to roll onto her left side,
- If applicable syntocinon should be turned off,
- IV increased to up blood pressure
- If still no recovery the doctor will be called
- This can occur after an epidural if the woman’s blood pressure has dropped and will pick up after IV is increased.
– Late decelerations:
- Drop in FHR after the peak in the contraction
- Never a good thing. Indicate that baby is not coping with labour.
– Fetal tachycardia:
- When FHR is higher than normal (110-160bpm)
- Indicates an infection/fever in either mom or baby. Can be a side effect of an epidural – epidural fever in the mother or a result of a very warm bath.
– Fetal bradycardia:
- When the baseline heart rate is less than 100 bpm for 3 minutes or more.
- Mild bradycardia of between 100-120 bpm is common in the following situations: Postdate gestation and OP or transverse presentations
- Severe prolonged bradycardia (less than 80 bpm for more than 3 minutes) indicates severe hypoxia. If the cause cannot be identified and corrected, immediate delivery is recommended.
Limitations of CTG
When first introduced CTG monitoring became standard for all women on admission to hospital. We have since learnt that when over used, on healthy low risk women, they can be detrimental in assisting women in having an intervention free, normal labour.
A 2017 Cochrane review links admission CTG with:
- Higher CTG use in labour
- Increase in FBS (fetal blood sampling) and EFM (electronic fetal monitor, with an electrode placed on the baby’s scalp)
- Higher likelihood of cesarean section (approx. 20% more likely)
- No decrease in secondary outcomes such as hypoxias
In conclusion they found no evidence of benefit for the use of admission CTG for low risk women on admission in labour. In fact women should be informed that admission CTG is likely associated with an increase in the incidence of caesarean section without evidence of benefit.
Fetal Blood Sampling:
This is sometimes done during labour for pH and lactate measurement. It is a second line technique used in cases of abnormal fetal heart rate. High lactates can be caused by stress. A sample of blood will be taken from the baby’s scalp and a EFM put on before the doctor decides what to do. Ideally FBS reduces the need for unnecessary caesarean sections.
As a doula your role is to support the woman and her partner, make sure she is the center of communication and understands the full picture and the results.
Understanding this information, although it is not your job to interpret it, gives you confidence as a doula.
- You can help your clients understand the CTG jargon and what doctors are looking for.
- You can give her physical and emotional support to help her labour in different (perhaps necessary) positions i.e. lying down.
- Offer to hold the monitors in place so that she can labour in different positions i.e. sitting on a ball.
- Ask the staff if you can turn the sound down.
Example CTG Printouts
- Each big square on the example CTG chart below is equal to one minute, so look at how many contractions occurred within 10 big squares.
- Individual contractions are seen as peaks on the part of the CTG monitoring uterine activity.
- The baseline rate is the average heart rate of the fetus within a 10-minute window.
- A normal fetal heart rate is between 110-150 bpm.
- Baseline variability refers to the variation of fetal heart rate from one beat to the next.
- It is a good indicator of how healthy a fetus is at that particular moment in time, as a healthy fetus will constantly be adapting its heart rate in response to changes in its environment.
- Accelerations are an abrupt increase in the baseline fetal heart rate of greater than 15 bpm for greater than 15 seconds. ¹
- The presence of accelerations is reassuring.
- Accelerations occurring alongside uterine contractions is a sign of a healthy fetus.
- Early decelerations start when the uterine contraction begins and recover when uterine contraction stops.
- This is due to increased fetal intracranial pressure. It therefore quickly resolves once the uterine contraction ends and intracranial pressure reduces.
- This type of deceleration is therefore considered to be physiological and not pathological.
- Late decelerations begin at the peak of the uterine contraction and recover after the contraction ends.
- This type of deceleration indicates there is insufficient blood flow to the uterus and placenta.
- The presence of late decelerations is concerning and fetal blood sampling for pH is indicated.
- If fetal blood pH is acidotic it indicates significant fetal hypoxia and the need for emergency C-section.