This baby sling turns sunlight into treatment for newborn jaundice

Daniel John slips his arms through the straps of his souped-up baby carrier, settles the harness against his chest and eases a newborn-sized doll behind the smoky blue–tinted window velcroed into the fabric. He checks the fit and smiles, confident that his medical sling will help turn a long-stalled idea into something tangible — and wearable — for parents who lack access to care for a common and readily reversible condition of early life.

Known as BiliRoo, this lightweight carrier is designed to treat neonatal jaundice, a condition that affects roughly 60 percent of newborns and 80 percent of preemies. It occurs when bilirubin — a yellow pigment in the blood — builds up faster than a baby’s body can clear it. In about 5 to 10 percent of cases, levels climb high enough that, without treatment, bilirubin can cross into the brain and cause permanent injury. Globally, severe jaundice is estimated to cause over 100,000 deaths each year, along with many more cases of long-term disability.

In modern hospitals, jaundice is usually a temporary nuisance: Babies are placed under electric blue lamps that help the body clear excess bilirubin, so levels fall and the problem goes away. In many parts of the world, however, phototherapy machines are scarce, forcing families to rely on sunlight instead. Yet, while the sun’s blue wavelengths can trigger the same bilirubin-breaking reaction, its ultraviolet rays can also damage sensitive skin and eyes, raising the specter of cancer.

It’s a risky compromise, one that John hopes caregivers won’t have to make. He described his patent-pending device and its early performance data January 14 in Pediatric Research.

Central to BiliRoo’s design is a transparent panel, positioned over the baby’s back, that blocks ultraviolet rays while letting therapeutic blue light through, mimicking hospital phototherapy. “It’s low cost, easy-to-use, simple and non-electric,” says John, a first-year medical student at the University of Michigan in Ann Arbor who founded a company, also called BiliRoo, to commercialize the concept.

As a bonus, treatment happens in a parent’s arms rather than inside a plastic crib. This eases the monitoring burden on overextended hospital staff, while allowing caregivers to go about their daily routines. It also promotes the type of skin-to-skin contact, known as kangaroo care, which strengthens bonding, regulates temperature and eases infant stress.

For John, the drive to build BiliRoo is deeply personal. He spent his childhood in midwestern Nepal, in the foothills of the Himalayas, where his father worked as a pediatrician and his mother as an industrial engineer. Power outages were routine, frequently knocking equipment offline at the local hospital.

When John moved to the United States and began studying mechanical engineering, he set out to design technologies that could function in low-resource settings like the one he knew growing up, places without steady electricity or modern infrastructure. “I knew I wanted to work in health care access,” he says. “And I saw the need for low-cost medical devices.”

John asked physicians in Nepal and sub-Saharan Africa what problems most urgently needed better solutions. One answer kept surfacing: neonatal jaundice. To John, filtered sunlight therapy looked like an underused workaround.

In Nigeria, studies from developmental pediatrician Bolajoko Olusanya and others had shown that the approach works: Newborns treated in filtered-sunlight tents and makeshift greenhouses fare just as well as those receiving standard phototherapy, with bilirubin levels falling safely in moderately jaundiced babies. But with little buy-in from government health officials, and substantial training of community health workers still needed to ensure safe and consistent use, the approach “has not been rolled out yet,” says Olusanya, executive director of the Centre for Healthy Start Initiative in Lagos, who was not involved in the study.

John’s goal is tobypass the need for dedicated sunlight-filtering rooms by putting the therapy directly in parents’ hands — or, rather, slung onto their bodies.

To build his first prototype, John methodically took commercial baby carriers apart, studying their straps, seams and load-bearing structure, before finally sewing sheets of optical filter film into scrap fabric. His older brother Stephen, also a physician-in-training — and a new father — became the first test user.

A practical challenge remained, though: Unlike in the types of structures that Olusanya studied, a parent carrying a baby is constantly shifting position. To be viable, the device would need to deliver therapeutic light across a range of angles, not just under ideal, straight-down sun.

John tested that idea in a university courtyard, finding that even with the carrier tilted at awkward angles, the sling consistently captured enough blue light to meet the standard for phototherapy, all while blocking more than 99 percent of harmful ultraviolet radiation.

Even with encouraging early tests, key questions remain about how reliably the device would work in everyday use. In real-world settings, sunlight is intermittent — clouds roll in, caregivers move indoors — raising uncertainty about whether babies in BiliRoos would consistently receive enough therapeutic light. And although the filters block ultraviolet radiation, prolonged exposure to warm sun could put vulnerable infants at risk of overheating or dehydration.

Those are exactly the kinds of issues that John now hopes to explore in clinical studies of his patent-pending device, which will soon include an additional filter section that can be pulled over the baby’s head. The first small batch of BiliRoos is being manufactured in Nepal, and John’s first trial with new parents and their young is slated to begin later this year in Ogbomoso, a city in southwestern Nigeria.

“I think it’s going to be a good device,” says Tina Slusher, a pediatric intensive care specialist at the University of Minnesota in Minneapolis, who led early trials of filtered sunlight therapy in Nigeria and is collaborating with John to test the BiliRoo. “There won’t be enough of the baby exposed to treat super-bad jaundice.” But for mild to moderate cases, she adds, “I think it’s a really good idea.”