Fetal heart monitoring mix ups - when the CTG picks up the maternal pulse

In a recent post Each Baby Counts report on anaesthetic care - Maternity safety depends on teamwork I commented on the latest report from the RCOG’s Each Baby Counts programme which reviewed the ways in which delays in anaesthetic care contributed to the tragic injury suffered during the births of 49 babies in 2015. The recurring theme of the report was that maternity safety depends on teamwork and that the anaesthetist is a key member of the team who must be included in communications and delivery suite planning of multiple, urgent deliveries if critical delays in treatment and consequent harm are to be avoided.

Obstetricians were reminded that they must take responsibility for communicating directly to the anaesthetist the urgency of the need for delivery, to enable the anaesthetist to prioritise patient visits and select appropriate anaesthetic, having regard to the speed with which delivery must be achieved and likelihood of escalation from one mode of delivery to another.

Maternity teams were unaware that the CTG was recording the maternal heart-rate

The report identified some other occasions where the anaesthetist’s involvement, whilst not solely causative of the injury, contributed to the adverse outcome for the child. In several cases the cardiotocograph (CTG) monitor was incorrectly assumed by the maternity team to be recording a normal fetal heart-rate (FHR). In fact, in the absence of a detectable FHR, it was picking up a maternal tachycardia (the mother’s elevated heart-rate).

It is reassuring to know that the Each Baby Count reviewers found that on most of the occasions when this occurred, the anaesthetist correctly pointed out what was happening to the other members of the maternity team. However, during one such incident, an anaesthetist was aware that the CTG was picking up the maternal pulse rather than the FHR but failed to communicate this to the unaware obstetric team, thereby missing an opportunity for emergency action to protect the baby.

The substitution of the maternal heart-rate for the FHR on the CTG trace is a rare occurrence but one that our cerebral palsy specialists at Boyes Turner see frequently and have ample experience in investigating. These cases generally involve a labour in which the fetus is struggling to take in sufficient oxygen. As the unborn baby becomes increasingly distressed, heart-rate abnormalities appear on the CTG trace, such as late decelerations, tachycardia (elevated baseline heart-rate), and reduced beat-to-beat variation, before the FHR gradually comes down again, declining into a terminal bradycardia during which the fetal brain is irrevocably damaged and, if undelivered, the unborn baby dies.

How do fetal and maternal heart-rate monitoring mix ups happen?

During labour and delivery the CTG monitor uses low power ultrasound Doppler signal to detect the fetal heart-beat, isolating it from the other movements within the mother’s abdomen. The CTG monitor also shows uterine activity (contractions). However, depending on the positioning of the external transducer on the mother’s abdomen or if the fetal heart becomes too weak and the FHR too slow for the transducer to pick up its signal, the CTG responds to the signal produced by the mother’s abdominal and uterine blood vessels and reproduces the maternal heart-rate on the CTG trace instead. The mother’s heart-rate would normally be slower than that of the fetus but during the stress of contractions during labour and delivery, her heart-rate increases, and the CTG reading of her tachycardia can be misinterpreted as a reassuringly normal fetal heart-rate by the maternity staff.

How can maternal and fetal heart-rate monitoring mix ups be avoided?

To avoid the possibility of fetal distress (which requires emergency action to deliver the baby) being masked by a misleading CTG reading, the NICE intrapartum guidelines and hospital protocols recommend regular, simultaneous checking of the maternal pulse and intermittent auscultation (listening) of the FHR throughout labour, to compare the mother’s heart-rate with the unborn baby’s and distinguish between the two. If there is any doubt about the FHR, a fetal scalp electrode should be attached to the unborn baby’s head to give a more reliable, direct, reading of the baby’s heart-rate.

Boyes Turner are experienced in these claims and can help

At Boyes Turner we have recently secured a substantial settlement for a young man who suffered profound hypoxic ischaemia at birth leading to dyskinetic cerebral palsy as a result of the maternity team’s failure to realise that the CTG was showing his mother’s heart-rate instead of his, and consequent delays in his delivery.

We support the RCOG’s efforts, by learning from mistakes through the Each Baby Counts programme, to raise standards of maternity care.

If you are caring for a child or young adult with cerebral palsy or birth-related brain injury contact our specialist lawyers by email at cerebralpalsy@boyesturner.com.

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