A full abdominal examination and palpation should be carried out and documented prior to commencing a CTG trace. Ensure the woman has emptied her bladder and is comfortable. Measure fundal height in centimetres, if not undertaken in previous two weeks, palpate and document the findings. The fetal heart should be auscultated with a Pinard stethoscope then doptone prior to commencing a CTG (NICE 2022).
Antenatal fetal monitoring (1292)
Warning
There is a recognised need for fetal monitoring for high-risk patients. Although there is no clear evidence that antenatal cardiotocography improves perinatal outcome (Grivell et al, 2015), the main purpose of CTG recordings is to identify when there is concern about fetal well-being to enable interventions to be carried out before the fetus is harmed (Beckmann 2014).
The aim of this guideline is to provide a standardised approach to fetal monitoring within the inpatient and outpatient setting for high-risk patients and to introduce the practice of computerised CTG.
Antepartum cardiotocography (CTG) should be considered in women of 26+0 gestation and above. All CTG traces should be peer reviewed by a trained team member. However, all normal CTG traces on fetuses below 32 weeks’ gestation should also be peer reviewed by an obstetrician prior to the CTG trace being stopped.
If the CTG is of poor quality, there should be early recourse to ultrasound location of the fetal heart rate (ideally within 20 minutes).
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.
Antenatal CTG | Reassuring | Non-reassuring |
Baseline rate (bpm) | 110-160 rate: | Less than 109 |
More than 161 | ||
Sinusoidal pattern for 10 minutes or more | ||
Variability | 5 bpm or more | Less than 5 bpm for more than 40 minutes |
Acceleration | Present | None for 40 minutes |
Decelerations | None | Unprovoked deceleration/s |
Decelerations related to uterine tightening (not in labour) | ||
Opinion | Normal CTG (all features reassuring) | Abnormal CTG (1 or more non-reassuring features) |
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 because 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.
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
If there are any concerns about the baby’s wellbeing, be aware of the possible underlying causes. Start one or more of the following conservative measures based on assessment of the most likely causes: encourage the woman to mobilise or adopt an alternative position (and to avoid being supine); offer intravenous fluids if the woman is hypotensive or tachycardic.
If conservative measures fail to resolve an abnormal CTG trace, immediate review by an obstetrician should be sought and a clear and concise plan documented.
Antepartum cardiotocography should be considered in women of 26+0 weeks gestation and above. Any CTG carried out before 26 weeks should be performed and interpreted with caution. The decision to do so must be based on an individual basis by a consultant obstetrician.
The fetal autonomic nervous system is immature and therefore the patterns of fetal heart rate which may be expected at later gestations are not present. Also there is increased possibility of signal loss and poor quality CTG at earlier gestations (Afors and Chandraharan, 2011).
Evidence suggests that the baseline fetal heart rate in preterm fetuses is at the higher end of the normal range for a term fetus for physiological reasons, but that this reverts to the range more consistent with term fetuses as gestation advances. However, any rate more than 160 bpm should be defined as tachycardia across all preterm gestational ages. The baseline variability may be reduced at preterm gestations for physiological reasons. However, at term, fetal heart rate variability is an important clinical indicator of fetal acid base balance and oxygenation of the autonomic nerve centres within the brain (NICE 2015).
Fetal heart rate decelerations are common and normal at very early preterm gestations (26 weeks and less) reflecting immature development of cardioregulatory mechanisms. The presence of shallow or short-lived decelerations in very preterm babies should not be considered necessarily as indicative of hypoxia when all other CTG features are reassuring.
From 32 weeks, baseline fetal heart rate and variability should be similar to that in term fetuses and accelerations with an amplitude of more than 15 beats from the baseline should be present as an indicator of fetal wellbeing. Decelerations can be interpreted as for the term fetus (NICE, 2015).
Midwives can sign off and discontinue CTGs providing they have completed an antenatal CTG proforma, a full assessment of the clinical picture with no abnormal findings and have had the CTG peer reviewed by a qualified team member.
All care should be provided in conjunction with local guidelines and medical plan.
All patients greater than 20 weeks gestation should have the fetal heart auscultated each day as a minimum as part of routine maternal observations. Where a patient is admitted to the antenatal ward, the admitting obstetrician must ensure a clear, defined plan stating the type and frequency of fetal monitoring is made and communicated to the midwifery staff.
A full antenatal examination should be carried out on admission to the ward including blood pressure, heart rate, oxygen saturations, temperature, respiratory rate and urinalysis. An abdominal examination, palpation and fetal heart auscultation should be carried out on admission.
There is little evidence regarding the timing and frequency of antenatal CTG monitoring within an inpatient setting. The following care plan has been devised from best practice within the antenatal ward setting.
Some of the most common reasons for admission to the antenatal ward are highlighted below. Any plan for fetal monitoring should be directed by a medical plan of care.
Antenatal CTGs must be reviewed promptly by a midwife or senior medical staff to decide whether monitoring should continue and to reassess the patient’s care plan. To maintain patient safety and accountability, CTGs must not be reviewed and signed off retrospectively.
If a CTG continues for more than 1 hour due to concerns or difficulty in interpreting normality, consider transferring the woman to the labour ward for continuous electronic fetal monitoring.
Reason for admission | Fetal monitoring |
Raised blood pressure | CTG on admission Twice daily CTG as a minimum. Increase frequency if clinically indicated or as documented in the medical plan |
Antepartum haemorrhage | CTG on admission. 6 hourly CTG whilst any PV loss. Increase frequency if clinically indicated or as documented in the medical plan |
Placenta praevia | CTG on admission. Daily auscultation of fetal heart Weekly CTG as a minimum if no bleeding. |
Suspected preterm labour | CTG on admission Twice daily CTG as a minimum. Increase frequency if clinically indicated or as documented in the medical plan |
Preterm rupture of membranes | CTG on admission Twice daily CTG. If <26 weeks auscultate twice daily. Increase frequency if clinically indicated or as documented in the medical plan |
Prolonged rupture of membranes >37 weeks for >24 hours | CTG on admission 6 hourly CTG until transferred to labour ward |
Spontaneous rupture of membranes on ward >37 weeks | Auscultate fetal heart immediately. CTG indicated if high risk for example induction of labour, polyhydramnios, preterm, unstable lie, high head, blood stained liquor, meconium-stained liquor |
Induction of labour | 6 hourly CTG until transferred to labour ward |
Early Labour | 6 hourly CTG as per latent phase guideline |
Vaginal birth after caesarean section (VBAC) | Minimum of 6 hourly CTG if in early labour Continuous CTG indicated when regular uterine activity establishes or if any complications such as bleeding or pain and transfer to labour ward. |
Diabetic women for steroids and/or slidingscale / VRIII prior to delivery. | CTG on admission. Daily CTG as a minimum. Increase frequency if clinically indicated or as documented in the medical plan |
Persistent altered fetal movements | CTG on admission. Twice daily CTG as a minimum. Increase frequency if clinically indicated or as documented in the medical plan |
Computerised CTG (cCTG) is a useful tool for antenatal monitoring from 26 weeks gestation. Saving Babies’ Lives Bundle 2 recommends the use of computerised CTG in antenatal fetal assessment as it is thought to reduce the risk of misinterpretation of the CTG due to human error. A comparison of computerised CTG (cCTG) vs traditional CTG showed a reduction in perinatal mortality however, a cCTG should not be used in isolation, instead a full clinical risk assessment should be carried out when interpreting a CTG.
Fetal heart rate is analysed by applying the Dawes Redman criteria to provide objective and reproducible assessment of fetal heart rate. Unlike traditional CTG interpretation, cCTG variability measures short term variation (STV), which is beat to beat variation of the fetal heart rate. STV differs from fetal heart rate variability. STV has been shown to be the best predictor of fetal wellbeing.
When to use a computerised CTG
Recommended for a SGA/FGR baby, particularly those with abnormal umbilical artery dopplers (PI >95th centile or AREDF)
Consider when an antenatal CTG assessment is required for any baby 26+0 weeks gestation and beyond
When a computerised CTG should NOT be used
Any uterine activity
Earlier than 26+0 weeks gestation
Use of computerised CTG should be at senior obstetrician discretion where additional ultrasound findings indicate a pre viable fetus (EFW <500g), confirmed or suspected lethal fetal anomaly.
If criteria are met for commencing a computerised CTG, see the GGC Right Decisions SOP guideline “Computerised CTG – Guidance on how to use and interpret”.
CTG monitoring is not required for women classified as low risk who are receiving IM opiate analgesia. These women should be reviewed regularly for the development of new antenatal or intrapartum risk factors that may change the need for fetal monitoring,
Women with additional risk factors should be commenced on CTG monitoring prior to administration of opiate analgesia to ensure fetal wellbeing. On completion of a normal CTG trace, this should be discontinued then the fetal heart should then be auscultated and documented one hour post administration.
Opiate analgesia crosses the placenta acting as a vasoconstrictor of the placental vasculature. This may result in reduced fetal tone, reduced fetal movements and reduced- to-absent fetal breathing movements (Kopecky et al, 2000). It is important to remember that a cardiotocograph trace may then show non-reassuring or abnormal baseline variability following the administration of opiate analgesia and should be considered when interpreting the CTG.