Portable Ultrasound Patch Monitors Babies in the Womb in Real Time

An international research team from Stanford Medicine, the University of California San Diego, and the University of Oxford has developed a novel wearable ultrasound patch capable of continuously monitoring blood flow in the fetus and the umbilical cord. The flexible device is applied directly to the pregnant woman’s abdomen and provides real-time information about the unborn child’s blood supply. The technology could open up new possibilities, particularly for high-risk pregnancies. The initial results on the development and validation of the device were published in the journal Nature Biotechnology.

Why Better Fetal Monitoring Is Urgently Needed

Current methods for monitoring high-risk pregnancies often reach their limits. This is particularly problematic in cases of pregnancy complications such as intrauterine growth restriction. In this condition, the fetus grows more slowly than expected, usually because it is not receiving sufficient oxygen and nutrients via the placenta and umbilical cord.

This complication affects an estimated ten percent of all pregnancies worldwide. In severe cases, the insufficient supply can become life-threatening. Doctors are then often faced with a difficult decision: If the baby is delivered too early, the risk of complications from prematurity increases. However, if one waits too long, a progressive lack of supply can lead to severe damage or even stillbirth. Continuous and reliable monitoring of blood flow could therefore be crucial for detecting changes early and better assessing the optimal time for medical intervention.

Limitations of Current Monitoring Methods

To date, high-risk pregnancies are usually monitored using Doppler ultrasound or cardiotocography. Both methods provide important information but have significant limitations. While conventional Doppler ultrasound can measure blood flow in the umbilical cord, it captures only brief snapshots. Additionally, the examination requires trained ultrasound technicians and special appointments. Continuous monitoring is therefore particularly difficult to implement for hospitalized high-risk patients.

Cardiotocography, which measures fetal heart rate and contractions, is also prone to errors. Fetal movements can cause false signals or result in the device temporarily failing to provide any usable data. As a result, the sensors must frequently be repositioned. Obstetrician Jane Chueh, who specializes in high-risk pregnancies, describes the current situation as very stressful—both for medical staff and for the pregnant women themselves. Especially with in-hospital patients, she notes, it is often difficult to obtain reliable readings multiple times a day.

How the New Ultrasound Patch Works

The newly developed ultrasound patch is about the size of a palm, flexible, and adheres directly to the mother’s abdomen. Currently, it is still connected via a cable to a computer that analyzes the ultrasound data. In the long term, however, the research team plans to develop a wireless version that could also enable monitoring at home. The development of the device presented the researchers with several technical challenges. Unlike many wearable health sensors, the patch does not measure data on the body’s surface but must capture information deep within the uterus. At the same time, both the mother and the fetus are constantly in motion.

To solve this problem, the scientists developed a special image segmentation algorithm. The system tracks in real time the area where the umbilical cord is connected to the placenta. This section remains relatively stable even when the fetus moves or the mother changes her position. This allows the patch to provide precise measurements without having to be constantly repositioned.

After initial tests on a simulation mannequin, the researchers first verified the device’s safety. In doing so, they ensured that neither excessive acoustic nor mechanical energy was transmitted to the fetus. The patch meets the safety standards of the U.S. Food and Drug Administration as well as those of other international ultrasound societies. The team then tested the system on 62 pregnant women and compared the results with conventional Doppler ultrasound devices. The data proved to be statistically equivalent.

The patch was able to visualize all three main vessels of the umbilical cord—two arteries and one vein—and additionally detect blood flow in important fetal vessels. Furthermore, the device was capable of measuring anatomical structures such as head circumference, abdominal circumference, and the length of the femur. This data can also be used to determine the estimated weight of the fetus, an important factor in diagnosing growth restriction. It was also noteworthy that the system functioned reliably even when the pregnant women were moving and provided stable measurements regardless of the position of the placenta.

Device Detected a Serious Complication Early

During the study phase, the research team made a particularly important observation. In one participant in her 28th week of pregnancy, the patch showed noticeable fluctuations in umbilical cord blood flow, even though the fetal heart rate initially appeared normal. At first, the scientists suspected a technical error. After several checks, however, it became clear that the device was working correctly. The attending physicians concluded that the fetus might not be receiving adequate blood supply.

Further examinations ultimately confirmed severe placental dysfunction. The patient was closely monitored, and four days later, the doctors decided to perform a cesarean section. The baby subsequently required treatment in the neonatal intensive care unit but developed well. For the researchers, this case was an important indication that the patch could detect potentially dangerous changes earlier than conventional monitoring methods.

Hope for a New Generation of Prenatal Monitoring

The developers see the ultrasound patch as having the potential for a completely new form of prenatal monitoring. Initially, the technology is intended primarily for use with high-risk inpatients, such as those with placental insufficiency, chronic high blood pressure, fetal growth restriction, or an increased risk of preterm birth. In these cases in particular, doctors often need to closely monitor the condition of the unborn child, as changes in blood flow can deteriorate rapidly.

In the long term, however, the research team is working on a wireless version of the device. The goal is to enable monitoring not only in the hospital but also at home. Pregnant women could then wear the patch for extended periods while ultrasound data is automatically transmitted to medical centers. Doctors could thereby track changes in fetal blood flow in near real time without patients having to constantly attend hospital appointments.

Such an approach could be particularly important for women in rural areas or for patients with limited mobility. At the same time, the technology could help shorten hospital stays and reduce the burden on pregnant women. Many women with high-risk pregnancies currently have to be hospitalized for days or weeks to undergo regular Doppler ultrasound examinations. A wearable system could make this monitoring significantly more flexible. The researchers therefore plan to conduct further studies covering a broader range of pregnancy complications. These include, among others, congenital heart defects in the fetus, chronic maternal conditions, preeclampsia, and various forms of placental disorders. Of particular interest to the scientists is whether the patch can detect early warning signs even before classic symptoms or changes in fetal heart rate occur.

Furthermore, in the long term, the technology could also provide new insights into fetal development. Since the patch continuously collects data rather than providing only brief snapshots, doctors could in the future better understand how the fetus’s blood flow, oxygen supply, and movement patterns change over the course of pregnancy. This could help provide more personalized care for high-risk patients and make medical decisions with greater precision. According to the doctors involved, the ultrasound patch could therefore be far more than just a new monitoring device. It could fundamentally change the management of high-risk pregnancies by detecting critical changes earlier and potentially avoiding unnecessary interventions. At the same time, the developers hope that the technology will make monitoring more comfortable for pregnant women and reduce the workload for medical staff, who have often had to spend a lot of time on repeated checks and repositioning existing monitoring devices.