Scientists have created a wearable ultrasound patch that can continuously monitor babies in the womb, with the hope that such devices could aid the early detection of complications during pregnancy.

The team behind the work say ultrasound-based techniques in place now have drawbacks: continuous monitoring of the baby’s heart rate and contractions of the womb using current methods leads to a high rate of false alarms, while the use of more conventional handheld devices for imaging is limited to a small number of scans during pregnancy, and must be carried out by a skilled operator.

“Current diagnosis devices are intermittent – that can only capture a snapshot of what’s going on with the baby,” said Prof Sheng Xu of Stanford University, a senior author of the work. “The patients can only do such measurements in the hospital. They miss a lot of information and data between the hospital visits.”

By contrast, Xu said, a wearable device can capture what is happening continuously, anywhere.

“You don’t miss any data, so that you can identify the baseline of the signals of each individual patient, analyse the change and pattern of these signals,” he said, which can lead to a unique diagnose or set of interventions.

Xu and his colleagues have created a wearable ultrasound patch that can be used for hours at a time to continuously image the foetus in the womb and track its blood flow in real time – including in moving structures such as the umbilical cord.

Although it is at present a proof-of-concept device that is tethered to external electronics and requires traditional ultrasound for initial placement, the team say the technology – called UPatch – is the first of its type.

“This paper marks a very important step [that] demonstrates how practically something like this can be done,” said Dr Antoniya Georgieva, a senior author of the study from the University of Oxford.

Writing in the journal Nature Biotechnology, the team reported how they used various electronic components and algorithms to solve key challenges – such the loss of signals as the baby moves in the womb, and weak signals that arise because of the depths of its blood vessels.

The researchers, many of whom are also involved in health tech companies, tested UPatch in trials in the US and UK.

In one test, involving 62 pregnant participants, the team compared blood flow measurements taken at a single time point from UPatch with those from standard handheld ultrasound devices.

“We observed close agreement between the wearable ultrasound patch and the conventional ultrasound device across these measurements,” said Tom Park, a PhD student at the UC San Diego Jacobs school of engineering and lead author of the work.

The team also used the device to continuously monitor foetal heart rate and blood flow measurements for 52 pregnant women, in one case with dramatic consequences.

“In a pre-eclamptic case, the UPatch revealed the severity of intrauterine growth restriction, leading to caesarean delivery to prevent stillbirth,” the team said.

Park said another insight from the device was that foetal blood flow measurements can fluctuate dynamically over time, including temporary changes that may not necessarily indicate a persistent problem.

“This highlights the limitation of relying only on brief intermittent scans,” he said.

Park said the team were now developing a wireless version of the tech: “Our long-term vision is a wearable ultrasound system that can be used continuously in daily life, including at home and during normal activities.”

Xu said wearables were particularly suited to low-resource areas, such as low and middle-income countries, while Georgieva said the benefits of such devices would be wide-ranging.

“The potential to prevent stillbirth directly is huge,” she said, adding that the device could also provide crucial academic insights.

“For us, having data like this can open the door to learning so much more about what makes some babies survive [in the womb] and others not.”