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A soft, adhesive ultrasound patch that continuously tracks fetal blood flow and anatomy may help clinicians detect complications earlier in high-risk pregnancies, according to a study published in Nature Biotechnology.

The device, called UPatch, was developed by engineers at the University of California San Diego (UCSD), in collaboration with the University of Oxford, Oxford, England. Unlike routine obstetric ultrasound, which provides only brief, intermittent scans during clinic visits, UPatch is designed for continuous, hands-free monitoring, without requiring a sonographer.

“This technology has the potential to democratize access to fetal surveillance, particularly in low-resource settings where specialist care is limited,” said first author Geonho (Tom) Park, a PhD student in chemical and nano engineering at UCSD.

Abdulla Al-Khan, MD, vice chair and division director of Obstetrics, Gynecology, and Women’s Health at Hackensack University Medical Center, Hackensack, New Jersey, who was not involved in the study, called the technology promising but still early-stage, emphasizing the need for further validation before routine clinical use.

How Does the UPatch Work?

The flexible adhesive patch is placed on the maternal abdomen and uses ultrasound waves to assess fetal structures and blood flow, including the umbilical cord and major fetal vessels.

It works by sending small electrical pulses to ultrasound transducers in the patch, which generate sound waves that pass through maternal tissue, reflect from fetal structures, and return to the same transducers. These signals are sent via a wired connection to an external computer for real-time imaging and blood flow analysis.

An autonomous algorithm continuously tracks the umbilical cord and monitors blood flow for hours, even as the mother or fetus moves. No sonographer is needed to reposition the probe, though initial placement is required. The signals are processed on a computer connected via a wire for real-time analysis.

“Fetal physiology is highly dynamic and can change over minutes or hours,” Park explained. Some complications develop intermittently and may go undetected between scans, sometimes leading to fetal injury or death, he said.

“We wanted to create a system that enables real-time monitoring of fetal well-being, rather than relying on isolated assessments,” he told Medscape Medical News.

The system performed similarly to sonographer measurements, with over 90% of readings within 2 mm of the target position and over 91% image accuracy, even during continuous movement.

Clinical Performance and Key Findings

Researchers evaluated UPatch in 62 pregnancies at UCSD Health and the University of Oxford, including normal pregnancies and those complicated by preeclampsia, gestational hypertension, gestational diabetes, fetal growth restriction, and size extremes. Continuous monitoring was performed in 52 women, with measurements taken every 15 seconds.

UPatch closely matched handheld ultrasound, showing strong correlation with fetal heart rate (r = 0.94) and blood flow ratios (r = 0.86), and only small differences in fetal biometry, including head and abdominal measurements, limb length, and estimated fetal weight.

During continuous monitoring, Doppler blood flow measures followed a more consistent pattern with gestational age and helped differentiate high-risk pregnancies from healthy ones. In contrast, fetal heart rate showed substantial overlap across groups.

“One of the most striking observations was how dynamic fetal blood flow patterns were over time,” Park noted. “These changes would be difficult to capture with routine intermittent scans.”

Repeated measurements over time also helped distinguish short-term fluctuations from more sustained changes that may indicate fetal or placental compromise.

A Case That Prompted Early Intervention

In one case, UPatch detected a sustained abnormal blood flow pattern consistent with placental dysfunction in a woman with preeclampsia at 28 weeks and 3 days.

“At first, I thought there might be a technical issue with the device because the finding was so unusual,” Park said. “But after careful checks, we confirmed the abnormality and immediately informed the clinical team.” The patient was transferred for higher-level care and delivered by cesarean 4 days later at 29 weeks. The baby required intensive care but recovered.

The researchers believe that continuous monitoring allowed timely detection of severe intrauterine growth restriction and likely prevented stillbirth.

Al-Khan, however, cautioned that not every abnormal signal detected through continuous monitoring should trigger intervention.

“An abnormal signal on a screen does not tell you whether to act, when to act, or how urgently,” he said. “Without a clear escalation pathway, this could lead to unnecessary interventions, including preterm deliveries, and the complications that come with them.”

What Comes Next?

The current UPatch is wired, limiting its use to inpatient settings, and requires an initial scan for correct placement. A wireless version is in development, with future iterations expected to integrate maternal signals such as blood pressure and oxygen saturation to improve risk assessment.

However, no reference ranges have yet been established for continuous fetal monitoring, making interpretation a central challenge. “Continuous fetal blood flow monitoring has not been performed at this scale before,” Park said. “We still need to define what level of variation is normal and what signals risk.”

Al-Khan agreed that this uncertainty is a barrier to safe clinical adoption. “We need clear definitions of what constitutes an abnormality and how clinicians should respond,” he said. Without that, he said, interpretation becomes uncertain and clinical decision-making more difficult.

He added that a broad rollout would be premature without further validation. “This is not something I would make available to every patient,” he said. “We need better patient selection, a defined clinical workflow, and prospective trials to determine whether continuous monitoring actually improves maternal and neonatal outcomes.”

The study was supported by Wellcome Leap (HER01430), the National Institutes of Health (1R01EB033464-01 and 1R01HL171652-01), and the Accelerating Innovation to Market program at the UCSD. Sheng Xu reported being a co-founder of Softsonics LLC. Mariana Tome, Lawrence Impey, and Antoniya Georgieva, all of the University of Oxford, reported being co-founders of Safer Birth Ltd. Aris T. Papageorghiou, also of the University of Oxford, reported being a senior scientific advisor to Intelligent Ultrasound Ltd. All other authors reported having no relevant conflicts of interest.