A Tiny Blood Vessel, a Big Decision: What Two New Studies Tell Families About Treating a Common Heart Finding in Premature Babies

Plain-language coverage of two 2026 clinical trials — the American PDA trial (Laughon and colleagues) and the European TREOCAPA trial (Rozé and colleagues) — on whether to treat the ductus arteriosus

The problem in plain terms

Before a baby is born, a small blood vessel called the ductus arteriosus lets blood skip past the lungs, which are not yet being used. Think of it as a temporary detour: in the womb the baby gets oxygen from the mother through the placenta rather than from breathing, so there is no reason to send much blood through the lungs, and this vessel provides the shortcut. Once a baby is born and starts to breathe, that detour is no longer needed and is meant to close. In babies born at full term, this vessel normally seals itself shut within a few days of birth. In babies born very early, it often stays open longer. When it stays open, doctors call it a patent ductus arteriosus, or PDA — "patent" simply means "open."

For a long time, an open ductus worried doctors. It tends to show up alongside serious complications of being born early, especially a lung condition called bronchopulmonary dysplasia (BPD for short), which is a kind of chronic lung injury in premature babies. Because the open vessel and the lung problems often appeared together, it seemed logical to close the vessel — and there are medicines that do exactly that, including acetaminophen (the same active ingredient as Tylenol or paracetamol), ibuprofen, and an older drug called indomethacin.

But "logical" is not the same as "proven." Closing the vessel and helping the baby turned out to be two different things, and two large studies published in 2026 have now shown this clearly. One, run across hospitals in the United States, is usually called the PDA trial [1]. The other, run across Europe, is called TREOCAPA [2]. This article explains what they found and what it means for families whose baby is in the neonatal intensive care unit, or NICU — the hospital unit that cares for premature and sick newborns.

Why doctors were already rethinking treatment

Even before these two studies, the evidence was pointing toward caution. A 2016 report from the American Academy of Pediatrics — the main U.S. professional group for children's doctors — had already advised against routinely using medicine to close the vessel, because there was no clear proof it helped [3]. Long-term records covering twenty years of premature babies showed that lung disease and other complications stayed common even as care improved [4]. And doctors had noticed something reassuring: in many babies, the vessel closes on its own without any treatment, sometimes even after the baby goes home [5].

There was also a puzzle hiding in plain sight. When researchers pooled together many earlier studies, they confirmed that the medicines really do close the vessel in most babies — roughly 7 or 8 out of every 10 treated. But the same review found that closing the vessel did not lower the number of babies who died or who developed serious complications [6]. Two more recent European studies pointed the same way: one (called BeNeDuctus) found that simply watching and waiting worked as well as early ibuprofen [7], and another (called Baby-OSCAR) found that treating large open vessels early did not reduce death or lung disease [8].

What the two new studies did

The two 2026 trials tackled the question from opposite directions, which is what makes them so useful together.

The American PDA trial [1] looked at babies who already had an open vessel that was causing concern. It included 482 babies born very early — between 22 and 28 weeks of pregnancy, when a full-term pregnancy is about 40 weeks. (The babies' middle birth weight was about 760 grams, a little under 1 pound 11 ounces.) Half the babies were given one of the closing medicines; the other half were simply watched closely, with medicine held in reserve only if the baby became unstable. This "watch closely and treat only if needed" approach is what doctors call expectant management.

The European TREOCAPA trial [2] tried prevention instead. It gave 778 very premature babies either acetaminophen, started within the first 12 hours of life, or a harmless saltwater placebo (a dummy treatment with no active medicine), to see whether getting ahead of the problem would help. Neither the families nor the doctors knew which babies got the real medicine until the study ended — a careful design that keeps the results trustworthy.

What they found

The American trial's headline result was striking enough that the researchers stopped the study early. Among babies who were watched rather than treated, the same proportion ended up with either death or lung disease as among those given medicine — about 8 in 10 in both groups, a difference too small to be meaningful [1]. But fewer of the watched babies died: about 4 in 100, compared with about 10 in 100 of the treated babies, by the time they reached the equivalent of 36 weeks of development [1]. In other words, leaving the vessel alone was tied to better survival, not worse. Serious infections leading to death were also less common in the watch-and-wait group. The lung disease itself was no different either way — treating the vessel did not protect the lungs.

The European trial showed the flip side of the same coin [2]. The preventive acetaminophen clearly worked at its narrow job: by the seventh day, the vessel had closed in about 71 of every 100 treated babies, compared with about 52 of every 100 who got the placebo. That is a real, large effect. And yet the babies were no more likely to survive without serious complications — about 66 in 100 with the medicine versus about 64 in 100 without it, again too close to call. On top of that, a liver-related side effect called cholestasis (a slowing of bile flow that can affect the liver) was more common in the babies given acetaminophen — about 6 in 100, compared with about 3 in 100 [2]. So a medicine that closed more vessels, faster, still did not help the babies overall, and carried a downside.

What this means for your baby

The most important takeaway is reassuring. If a doctor tells you that your premature baby has an open ductus arteriosus and recommends watching it rather than rushing to treat it, that is now backed by strong evidence — and, in the American study, watching was actually linked to better survival [1]. A preventive medicine given to every very premature baby did not help and caused more side effects, so that approach is not recommended either [2]. This fits with what the latest 2025 guidance from the American Academy of Pediatrics also reflects [9].

A few things are worth keeping in mind. These studies looked at babies whose open vessel was a concern but who were otherwise stable. They did not include the small number of babies who were already seriously unwell from the open vessel, because doctors agreed those babies should still be treated [1]. So "watch and wait" is the right starting point for most babies, but your medical team will still step in if your baby needs it — that judgment, often guided by an ultrasound of the heart (an echocardiogram, a painless scan that lets doctors see the vessel), remains important.

It also helps to know that an open vessel is, for most babies, a finding to monitor rather than an emergency. Many of these vessels close on their own [5], and how a premature baby does overall depends far more on how early they were born and on complications like infection and lung disease than on this one vessel [4]. Doctors can now confirm a vessel has closed and still recognize that this alone does not predict how well the baby will do [2][6].

Questions doctors are still working on

Science rarely closes a question completely, and these studies leave a sensible next step. Researchers still want to know whether a particular group of babies — for example, those with an especially large open vessel that is clearly straining the heart or lungs — might benefit from treatment, even if most babies do not. The American team is also following its babies to age two to make sure that the better survival with watchful waiting also means healthy development over time [1]. The lung-disease definition used to measure outcomes is itself carefully graded by severity, so future studies can compare results fairly [10].

For now, the message families can hold onto is a calm and reassuring one: for most very premature babies, an open ductus arteriosus does not need to be chased with medicine, watching it closely is a sound and well-studied choice, and your care team will step in and act if your baby turns out to be the one who needs something more.

References

  1. Laughon MM, Thomas SM, Watterberg KL, et al. Expectant Management vs Medication for Patent Ductus Arteriosus in Preterm Infants: The PDA Randomized Clinical Trial. JAMA. 2026;335(7):588-599. doi:10.1001/jama.2025.23330 ↩
  2. Rozé JC, Cambonie G, Flamant C, et al. Prophylactic Treatment of Patent Ductus Arteriosus With Acetaminophen: A Randomized Clinical Trial. JAMA Pediatr. 2026;180(4):374-383. doi:10.1001/jamapediatrics.2025.6150 ↩
  3. Benitz WE; Committee on Fetus and Newborn, American Academy of Pediatrics. Patent Ductus Arteriosus in Preterm Infants. Pediatrics. 2016;137(1):e20153730. doi:10.1542/peds.2015-3730 ↩
  4. Stoll BJ, Hansen NI, Bell EF, et al. Trends in Care Practices, Morbidity, and Mortality of Extremely Preterm Neonates, 1993-2012. JAMA. 2015;314(10):1039-1051. doi:10.1001/jama.2015.10244 ↩
  5. Semberova J, Sirc J, Miletin J, et al. Spontaneous Closure of Patent Ductus Arteriosus in Infants ≤1500 g. Pediatrics. 2017;140(2):e20164258. doi:10.1542/peds.2016-4258 ↩
  6. Mitra S, Florez ID, Tamayo ME, et al. Association of Placebo, Indomethacin, Ibuprofen, and Acetaminophen With Closure of Hemodynamically Significant Patent Ductus Arteriosus in Preterm Infants: A Systematic Review and Meta-analysis. JAMA. 2018;319(12):1221-1238. doi:10.1001/jama.2018.1896 ↩
  7. Hundscheid T, Onland W, Kooi EMW, et al. Expectant Management or Early Ibuprofen for Patent Ductus Arteriosus. N Engl J Med. 2023;388(11):980-990. doi:10.1056/NEJMoa2207418 ↩
  8. Gupta S, Subhedar NV, Bell JL, et al. Trial of Selective Early Treatment of Patent Ductus Arteriosus With Ibuprofen. N Engl J Med. 2024;390(4):314-325. doi:10.1056/NEJMoa2305582 ↩
  9. Committee on Fetus and Newborn, American Academy of Pediatrics. Patent Ductus Arteriosus in Preterm Infants. Pediatrics. 2025;155(5):e2025071425. doi:10.1542/peds.2025-071425 ↩
  10. Jensen EA, Dysart K, Gantz MG, et al. The Diagnosis of Bronchopulmonary Dysplasia in Very Preterm Infants. An Evidence-based Approach. Am J Respir Crit Care Med. 2019;200(6):751-759. doi:10.1164/rccm.201812-2348OC ↩