Antenatal Fetal Monitoring, Inpatients (641)

Some of the most common reasons for admission to the antenatal ward are highlighted below. Any plan for fetal monitoring may be directed by a medical plan of care.

Antepartum cardiotocography (CTG) should be considered in women of 26+0 gestation and above. CTG’s carried out before 28 weeks should be performed and interpreted with caution, the decision to do so must be made on an individual basis by a senior obstetrician. The fetal autonomic nervous system is not mature 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). 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 during the shift.

If CTG is of poor quality there should be early recourse to ultrasound location of the fetal heart rate (ideally within 20 minutes).

A full abdominal examination 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, palpate and document the findings. The fetal heart should be auscultated with a Pinard or doptone prior to commencement (Perinatal Institute 2018).

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.

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 and 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.

All cardiotocograph traces must be peer reviewed prior to completion by either a member  of midwifery staff or an obstetrician and documented appropriately. 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.

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).

All care should be provided in conjunction with local guidelines and medical plan

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.

A full antenatal examination should be carried out on admission to the ward including blood pressure, heart rate, oxygen saturations, temperature, respiratory rate, urinalysis and abdominal examination and fetal heart rate. A CTG trace should be carried out where indicated.

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).

Although a CTG may not be indicated in low risk women, in order to ensure fetal wellbeing, CTG monitoring should be commenced prior to administration. On completion on a normal CTG trace, this should be discontinued then the fetal heart should then be auscultated and documented one hour post administration. 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.