Fetal monitor/cardiotocograph (CTG) - adverse outcomes still reported
(All) adverse outcomes are still reported when CTG traces appear normal - this replaces alert SN 2002(23) issued August 2002. (MDA/2010/054)
Device
Fetal monitor/cardiotocograph (CTG).
This replaces SN 2002(23) issued August 2002.
Cardiotocographs (CTGs) monitor the fetal heart rate with an ultrasound transducer and maternal contractions with a toco (strain gauge) transducer. During labour, they give an indication of how the fetal heart rate (FHR) is responding to the stress caused by maternal contractions.
Problem
Adverse outcomes are still being reported in the presence of CTG traces that appear normal.
For example, the display of double maternal heart rate (MHR x 2) can be falsely reassuring.
Cardiotocographs assist in the management of labour, but should not be relied upon in isolation to monitor the condition of the fetus.
The NICE clinical guideline 55 ‘Intrapartum care’ (chapter 1.12.2 Interpretation of FHR traces/cardiotocographs) classifies four FHR trace features: ‘Baseline’, ‘Variability’, ‘Decelerations’ and ‘Accelerations’.
It also gives values for ‘Reassuring’, ‘Non-reassuring’ and ‘Abnormal’.
It then uses these features to define ‘Normal’, ‘Suspicious’ and ‘Pathological’ FHR traces. See appendix for details.
These guidelines also recommend that the maternal pulse is palpated if a FHR abnormality is detected, in order to differentiate the two heart rates (sections 1.6.13 observations during first stage of labour and 1.7.6 second stage).
The problem is that adverse incident reports often state that the fetal heart rate was in the normal range and staff only suspect a FHR abnormality after the event. CTG users should be aware of the limitations and artefacts that can occur, which have important implications for interpretation.
Below are two examples of situations that have occurred in UK hospitals.
Example 1: In two recently reported incidents the CTG trace showed the FHR was around 160 bpm. The maternal pulse had been noted earlier at around 80 bpm. In one case the baby was stillborn. In the other the baby required extensive resuscitation. It was later suspected that in both cases the trace was showing double maternal rate and was falsely reassuring.
Explanation: The fetus can move out of the ultrasound field or in extreme cases the fetal heart can stop beating. The ultrasound may then pick up the maternal pulse from the aorta, iliac or uterine artery. The FHR displayed will then actually be the maternal heart rate, MHR. Sometimes the maternal artery movement is double counted so MHR x 2 is displayed. This can be within the same range as the expected FHR and can be more difficult to interpret. The resulting trace shows reactivity and variability due to MHR changes and muscle contractions and can be difficult to distinguish from FHR.
Example 2: It has been observed that half the fetal heart rate (FHR ÷ 2) can be displayed.
Explanation: This can be due to difficulty in extracting the weak fetal heartbeat Doppler ultrasound signal from the noisy maternal environment.
Action
Local procedures for maintaining expertise should ensure that relevant clinical staff:
- do not rely solely on the CTG trace for fetal wellbeing and are aware of limitations and artefacts, such as double maternal heart rate being displayed
- confirm fetal heart rate using independent means (Pinard or hand held Doppler) if there is any clinical uncertainly
- read the manufacturer’s instructions for use
- are familiar with the NICE clinical guideline for intrapartum careNICE clinical guideline for intrapartum care.
Check the presence of a fetal heartbeat by independent means (eg Pinard stethoscope, hand-held Doppler):
a) before starting CTG monitoring
b) after a period where the FHR trace is reassuring and then a change occurs
c) after a period where the FHR trace is non-reassuring and then appears to recover.
Consider maternal ECG or pulse oximetry (SpO2) monitoring when using CTG monitors incorporating cross correlation software. This can alert the user when the FHR is the same value as the MHR.
Although an alert may not be generated if the FHR trace is constantly showing MHR x2, the recording of maternal pulse makes it easier for the user to check whether the FHR display could be MHR x 2.
Distribution
This MDA has been distributed to:
- NHS trusts in England (chief executives)
- HSC trusts in Northern Ireland (chief executives)
- NHS boards in Scotland (chief executives)
- NHS boards and trusts in Wales (chief executives)
- Primary care trusts in England (chief executives)
Onward distribution
Please bring this notice to the attention of all who need to know or be aware of it. This may include distribution by:
Trusts to:
CAS and SABS (NI) liaison officers for onward distribution to all relevant staff including:
- Anaesthetists
- Clinical governance leads
- Medical director
- Midwifery staff
- Nursing executive directors
- Obstetricians
- Risk managers
Care Quality Commission (CQC) (England only) to:
The MHRA considers this information to be important to:
- Hospitals in the independent sector
- Private medical practitioners
Primary care trusts to:
CAS liaison officers for onward distribution to all relevant staff including:
- Community midwives
Feedback
If you have any comments or feedback on this Medical Device Alert, please email us at: dts@mhra.gov.uk
Appendix
(71Kb)
England
If you are in England, please send enquiries about this notice to the MHRA, quoting reference number MDA/2010/054 or file number 2010/002/005/291/001.
Technical aspects
Geoff Smith or Catriona Blake
Medicines & Healthcare products Regulatory Agency
Market Towers
1 Nine Elms Lane London
SW8 5NQ
Tel: 020 7084 3198/3219
Fax: 020 7084 3209
Email: geoff.smith@mhra.gov.uk or catriona.blake@mhra.gov.uk
Clinical aspects
Jonathan Plumb
Medicines & Healthcare products Regulatory Agency
Market Towers
1 Nine Elms Lane London
SW8 5NQ
Tel: 020 7084 3128
Fax: 020 7084 3111
Email: jonathan.plumb@mhra.gov.uk
How to report adverse incidents
Please report via our website: Reporting adverse incidents involving medical devices.
Further information about CAS can be found on the Central Alerting System website .
Northern Ireland
Alerts in Northern Ireland will continue to be distributed via the NI SABS system.
Enquiries and adverse incident reports in Northern Ireland should be addressed to:
Northern Ireland Adverse Incident Centre
Health Estates
Estate Policy Directorate
Stoney Road
Dundonald
Belfast
BT16 1US
Tel: 02890 523 704
Fax: 02890 523 900
Email: NIAIC@dhsspsni.gov.uk
Northern Ireland Adverse Incident Centre (NIAIC)
SAN2002(23) was published in Northern Ireland under SN(NI)2002/28.
How to report adverse incidents in Northern Ireland
Please report directly to NIAIC, further information can be found on the NIAIC website .
Further information about SABS can be found on the SABS website .
Scotland
Enquiries and adverse incident reports in Scotland should be addressed to:
Incident Reporting and Investigation Centre
Health Facilities Scotland
NHS National Services Scotland
Gyle Square
1 South Gyle Crescent
Edinburgh
EH12 9EB
Tel: 0131 275 7575
Fax: 0131 314 0722
Email: nss.iric@nhs.net
Health Facilities Scotland - Incident Reporting and Investigation Centre .
Wales
Enquiries in Wales should be addressed to:
Dr Sara Hayes
Senior Medical Officer
Medical Device Alerts
Welsh Assembly Government
Cathays Park
Cardiff
CF10 3NQ
Tel: 029 2082 3922
Email: Haz-Aic@wales.gsi.gov.uk
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