MHRA Curbs Wireless Fetal Monitor Signal Mix-Ups

MHRA has told hospitals to keep wireless fetal heart-rate monitors on separate radio channels after a safety review found that two devices sharing a channel can, in rare circumstances, cross signals — displaying one patient's fetal heart rate on a different patient's monitor. The alert, Device Safety Information notice DSI/2026/012, published 17 September 2026, is precautionary: MHRA says it has no confirmed case of a patient harmed by this specific issue, but is acting on the risk before one occurs.

A crowded, narrow radio band

Wireless CTG systems free a labouring patient from a cable tether to a bedside monitor, transmitting fetal heart rate and contraction data over radiofrequency telemetry instead. MHRA's review found that this convenience carries a coexistence problem: the devices typically operate within the Industrial, Scientific and Medical (ISM) radio band, which offers only a limited number of channels. When multiple wireless CTG units are in use within range of each other and land on the same channel without sufficient separation, MHRA found evidence — drawn from incident reports and feedback from other health bodies — of devices “capturing fetal heart rate from a different device where devices are operating on the same RF channel and are an insufficient distance apart.” The practical result, in the rare cases where it occurs, is a monitor displaying a trace that belongs to someone else's baby.

Why crossover matters on a labour ward

A cardiotocograph trace is a primary tool clinicians use to judge whether a baby is tolerating labour well or showing signs of distress that call for intervention. If a trace displayed on one patient's monitor is actually a different patient's data — even briefly, and even if the underlying reading was itself normal for the other baby — a clinician could reasonably misjudge the monitored patient's status: missing a genuine sign of distress that the crossed-in trace happens to mask, or, conversely, acting on a false alarm that belongs to someone else. MHRA's notice frames the risk in exactly those terms: misinterpretation of CTG traces leading to inappropriate clinical decisions with potential for adverse consequences. The alert does not identify a specific manufacturer or product; it applies across wireless CTG systems that share the RF-coexistence characteristics MHRA's review examined.

What MHRA is telling maternity units to do

• Ensure two or more wireless CTG devices in use near each other are not operating on the same RF channel, unless there is enough physical distance between them to prevent crossover or interference.
• Treat any unexplained change in a trace, or a loss of signal, as a possible monitoring failure — not as reassurance — and promptly escalate to confirm the reading through a reliable alternative.
• The notice is addressed to NHS trusts, maternity units, and clinical/biomedical engineering teams responsible for configuring and maintaining wireless telemetry equipment, as well as to manufacturers.
• MHRA's alert followed a wider pattern of reporting: the Sunday Telegraph's 20 September coverage, headlined “Wireless foetal monitors detect wrong babies,” brought the precautionary warning to public attention days after MHRA published it, describing NHS units being told to follow new operating precautions.

Frequently asked questions

What did MHRA warn about?

In Device Safety Information notice DSI/2026/012, published 17 September 2026, MHRA said a review of wireless cardiotocography (CTG) monitoring systems — which track fetal heart rate and uterine contractions over radiofrequency telemetry — found the devices can suffer signal crossover, erroneous traces, and signal dropouts. In rare circumstances, one patient's fetal heart rate can display on a different, nearby CTG monitor operating on the same RF channel.

Has this caused patient harm?

MHRA describes the alert as precautionary and says it has no confirmed case of patient harm resulting from this specific RF crossover issue. The concern is the risk: a clinician acting on a trace that actually belongs to a different patient could make an inappropriate clinical decision in a labour ward.

Why does this happen?

Wireless CTG telemetry typically operates within the Industrial, Scientific and Medical (ISM) radio band, where only a limited number of channels are available. MHRA said signal crossover can occur when two or more wireless CTG devices operate on the same channel and are not far enough apart.

What is MHRA telling hospitals to do?

Ensure that two or more wireless CTG devices in use nearby are not operating on the same RF channel unless there is sufficient distance between them to prevent crossover, and treat any unexplained change in a trace or loss of signal as a possible monitoring failure — escalating promptly to confirm the reading using a reliable alternative rather than assuming the displayed trace is accurate.