When reviewing the cardiotocograph (CTG) trace it is important to assess and document any contractions and all four features of fetal heart rate;
- Baseline rate
- Baseline variability
- Presence or absence of decelerations
- Presence of accelerations
It is also important to record maternal heart rate. Where there is any difficulty in categorising or interpreting a CTG trace, a review by a senior midwife or obstetrician should be obtained.
The RCOG Green-top Guideline on the management of reduced fetal movements recommends that interpretation of the antenatal CTG fetal heart rate pattern can be assisted by adopting the NICE classification of fetal heart rate features as indicated in their intrapartum care guideline. Therefore, as is the case when classifying intrapartum CTGs, it would seem reasonable to use a structured pro forma to ensure the use of consistent terminology. However, using an intrapartum pro forma is not appropriate as it acknowledges that some decelerations are acceptable in labour, which clearly cannot be the case for antenatal CTGs where there are no contractions.
Baseline rate (beats/minute) This is the average fetal heart rate within a ten minute window.
Baseline variability (beats/minute) This refers to the variation of fetal heart rate from one beat to the next. Variability occurs as a result of the interaction between the nervous system, chemoreceptors, baroreceptors and cardiac responsiveness.
Accelerations are an abrupt increase in the baseline fetal heart rate of greater than 15 bpm for greater than 15 seconds. The presence of fetal heart rate accelerations, even with reduced baseline variability, is generally a sign that the baby is healthy.
Decelerations are an abrupt decrease in the baseline fetal heart rate of greater than 15 bpm for greater than 15 seconds.
Any decelerations on an antenatal CTG should be considered abnormal and prompt medical review.
This pro forma has been adapted from PROMPT training and should be utilised for the classification of CTG traces in non-labouring women only.
|Baseline rate (bpm)
||Less than 109
|More than 161
|Sinusoidal pattern for 10 minutes or more
||5 bpm or more
||Less than 5 bpm for more than 40 minutes
||None for 40 minutes
|Decelerations related to uterine tightening (not in labour)
||Normal CTG (all features reassuring)
||Abnormal CTG (1 or more non-reassuring features)
Antenatal CTG classification
Normal: A CTG where all four features fall into the ‘reassuring’ category.
Abnormal: A CTG with any non reassuring features (including any decelerations)
When an abnormal CTG is identified, it should be reviewed by an experienced obstetrician as soon as possible (within 30 minutes) to make a clear individualised action plan