When a Scan Suggests a Narrowed Aorta: What Families Need to Know

Four studies from 2025 and 2026 on why this heart problem is hard to see before birth, and how doctors are trying to protect babies without treating healthy ones

When a pregnancy scan suggests that a baby's main artery may be narrowed, families are often asked to prepare for heart surgery after birth. Yet in the largest series published in 2025 and 2026, about two thirds of those babies were born with a normal artery. Four new studies examine why this diagnosis is so hard to make before birth, and how doctors are trying to protect affected babies without treating healthy ones unnecessarily.

Why a narrowed aorta is so hard to see before a baby is born

The aorta is the large artery that carries blood from the heart to the rest of the body. In some babies, a short section of it is too narrow — a condition called coarctation of the aorta. It is one of the more common serious heart problems present at birth, and it can be life-threatening if it is not found in time.

The reason it hides so well before birth comes down to how a baby's circulation works in the womb. While a baby is still developing, a small blood vessel called the ductus arteriosus provides a bypass route around the narrowed section. Blood simply takes the detour. The narrowing is there, but it is not yet causing any obstruction, so there is nothing dramatic for a scan to show. Doctors are left looking for indirect hints instead: the right side of the heart looking a little larger than the left, the main arteries looking mismatched in size, the suspicious section looking slightly small for the baby's age.

Those hints are genuinely useful, but they are not the problem itself — they are shadows of it. And in the days after birth, when the bypass vessel naturally closes, the situation changes completely. If the narrowing is real, blood flow to the lower body suddenly drops and the baby can become very unwell within hours. If the narrowing was never really there, nothing happens at all.

What this has meant for families until now

For most of the past twenty-five years, the medical response to this uncertainty has been to assume the worst and plan accordingly. That approach was built on solid reasoning. A study from Oxford published in 2002 showed that babies whose coarctation was found before birth survived better and were less unwell than those diagnosed afterwards [1], and no one has seriously argued the opposite since. Knowing in advance genuinely saves lives.

The cost, though, has fallen on a large number of families whose babies were healthy all along. A suspicion raised at a mid-pregnancy scan typically means being referred to a specialist centre, giving birth far from home, having the baby admitted to intensive care, starting a medicine that keeps the bypass vessel open, and waiting through days of repeated scans while mother and baby are separated [2][3]. A large review published in 2017 gathered the best available warning signs on ultrasound [4], but even with all of them, roughly one in every three or four babies flagged before birth turns out not to have coarctation — and in the specialist clinics that published this year, closer to two out of every three [5]. Doctors have long known this. What they have lacked is a reliable way to tell which babies are which.

What the four new studies looked at

Three of the four studies asked the same question from different angles: among babies already under suspicion, is there anything that separates the ones who really have coarctation from the ones who do not?

A team in Guangzhou, China, reviewed 222 pregnancies in which coarctation had been suspected between 2013 and 2024, and followed every baby for at least six months after birth. Sixty-nine needed heart surgery; 153 were fine [5]. A second team, in Turkey, looked back over 9,000 fetal heart scans performed between 2020 and 2025 and found 10 babies with this suspicion and no other heart problems; 7 of them had coarctation [6]. A third team, in Fujian, China, compared 29 babies whose suspicion proved false with 15 whose did not, alongside 50 babies with normal scans [7]. The fourth study is a review from the University of Birmingham in the United Kingdom, which asks the opposite question: what happens to babies whose coarctation nobody suspected at all [8]?

The measurements doctors have relied on could not tell the two groups apart

The clearest result from these studies is a disappointing one, and it matters. The measurements most often quoted to families — the right side of the heart being bigger than the left, the main arteries being mismatched, the suspicious segment measuring small — were abnormal in almost everyone who had been flagged. But they were just as abnormal in the babies who turned out to be healthy as in those who needed surgery.

In the Guangzhou study, the ratio comparing the two lower chambers of the heart was essentially identical in both groups. In the Fujian study, four separate standard measurements all failed to separate the groups. And in the Turkish study, every one of the ten babies had been selected because the narrow segment measured well below normal — yet three had no coarctation.

This does not mean the measurements are worthless. It means they are good at answering "should we be worried?" and poor at answering "how worried should we be?" That distinction is worth holding on to if you are ever handed a number during a scan.

A harmless flap of tissue that can imitate the problem

The Fujian team took a different approach: instead of asking what predicts coarctation, they asked what else could produce the same picture. Their answer is a small, ordinary piece of anatomy. Every baby in the womb has a flap of tissue over an opening between the two upper chambers of the heart. In some babies this flap is unusually long and floppy. When it swings about, it can briefly get in the way of blood flowing into the left side of the heart — which makes the left side look smaller than the right, exactly the appearance that raises suspicion of coarctation.

When the researchers measured how far this flap bulged relative to the size of the chamber it sat in, the babies with a false alarm stood out clearly from the babies with real coarctation, while the standard measurements did not [7]. Importantly, this floppy flap causes no harm. After birth it settles, the circulation rebalances, and the aorta grows normally.

This is still early work — only 15 confirmed cases, and different doctors measuring the same images did not always agree. But it names something useful. A hint that looked like a disease may have an innocent explanation, and it is one a specialist can look for.

A simple shape on the screen that may help

The Turkish study offers something different again: not a calculation but a shape. When the aorta and the bypass vessel join normally, they form a recognisable "Y" on a particular view. In the babies who went on to need surgery, that Y was missing — the two vessels met at a sharper, distorted angle instead. The sign was absent in every baby who had coarctation and present in babies who did not [6].

The appeal is its simplicity: no measurements, no calculations, just a shape that a sonographer either sees or does not see. Two specialists reviewing 200 normal scans agreed about it most of the time. But the study rests on just seven confirmed cases, and one baby without the Y sign turned out to have a normal aorta. It is a promising idea awaiting a much larger test.

Why the newborn oxygen test can miss this particular heart problem

Most babies in high-income countries now have their oxygen levels checked with a small sensor on the hand and foot before going home. This simple test finds many serious heart conditions early and has reduced deaths from them by more than a third [9][8]. In 2025 the American Academy of Pediatrics updated how the test is interpreted [10], and our companion article on newborn oxygen screening explains how it works.

Coarctation, unfortunately, is the condition this test finds least well. Because the bypass vessel is often still open when the test is done, the oxygen level can look completely normal. A Swedish study of 38 babies with severe narrowing of the aorta found that 21 of them — more than half — went home without a diagnosis, and more than half of those became seriously unwell before they came back [11]. Researchers are testing an additional measurement from the same sensor that may help, but it currently flags too many healthy babies to be adopted.

This is the reason clinicians still check a baby's leg pulses and blood pressure by hand, and the reason parents are asked to seek urgent help if a newborn feeds poorly, breathes fast, looks mottled or grey, or becomes difficult to wake — even after a normal check.

What families should know if this comes up at a scan

If a scan raises this possibility, three things are worth knowing. A suspicion is not a diagnosis, and more babies in this situation are born without coarctation than with it. There is a plan, and increasingly a written one: hospitals in Chicago and Washington, DC published graded pathways in 2026 that match the level of concern to the level of care, so that lower-risk babies can stay with their mothers and have a scan after birth rather than being started on medicines they may not need [12][13][14]. And the uncertainty is temporary — the answer usually arrives within the first days of life.

It is also normal for this period to be frightening, and the strain of a pregnancy spent waiting for an answer is real; our article on mental health for parents in the newborn intensive care unit may be helpful. Families often ask what coarctation would mean in the longer term if it is confirmed. Results after repair in the newborn period are generally good, though researchers continue to study how heart conditions present from birth affect a child's development, a subject we cover in our article on the developing brain in congenital heart disease.

What researchers are working on next

The honest summary of this year's work is that three promising ideas have appeared and none is ready. Each comes from a single hospital, each rests on a small number of confirmed cases, and none has yet been tested somewhere else. What researchers need now is a larger study across many hospitals that enrols families at the moment the suspicion is raised, records all of these features in the same baby, and measures something more meaningful than diagnostic accuracy: how many healthy babies were spared unnecessary treatment, without a single baby with a real narrowing being missed. Alongside that, work continues on making the newborn oxygen check better at catching the babies whom nobody suspected in the first place. Neither problem is solved. Both are being taken seriously, and families who find themselves in this situation are being cared for under plans that are noticeably more thoughtful than they were even five years ago.

References

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  2. Hede SV, DeVore G, Satou G, Sklansky M. Neonatal management of prenatally suspected coarctation of the aorta. Prenat Diagn. 2020;40(8):942-948. doi:10.1002/pd.5696 ↩
  3. Arya B, Maskatia SA. Coarctation of the aorta: prenatal assessment, postnatal management and neonatal outcomes. Semin Perinatol. 2022;46(4):151584. doi:10.1016/j.semperi.2022.151584 ↩
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  5. Zhao X, Yu Y, Zeng S, et al. Predictive model integrating two-dimensional ultrasound indicators and hemodynamic features for fetal coarctation of the aorta. BMC Pediatr. 2026;26(1):420. doi:10.1186/s12887-026-06786-7 ↩
  6. Daglar HK, Kaymak D. The "Y sign" as a novel qualitative marker for prenatal detection of aortic coarctation: a retrospective cohort study. BMC Pregnancy Childbirth. 2025;25(1):1132. doi:10.1186/s12884-025-08376-4 ↩
  7. Li L, Li Y, Zhang S, et al. Ultrasound characteristics of an isolated redundant foramen ovale flap in fetuses and its differential diagnosis from aortic coarctation. J Clin Med. 2026;15(8):3166. doi:10.3390/jcm15083166 ↩
  8. Ewer AK. Pulse oximetry screening in the newborn: can modifications to the screening algorithm improve detection? Int J Neonatal Screen. 2026;12(3):53. doi:10.3390/ijns12030053 ↩
  9. Plana MN, Zamora J, Suresh G, Fernandez-Pineda L, Thangaratinam S, Ewer AK. Pulse oximetry screening for critical congenital heart defects. Cochrane Database Syst Rev. 2018;3:CD011912. doi:10.1002/14651858.CD011912.pub2 ↩
  10. Oster ME, Pinto NM, Pramanik AK, et al. Newborn screening for critical congenital heart disease: a new algorithm and other updated recommendations: clinical report. Pediatrics. 2025;155(1):e2024069667. doi:10.1542/peds.2024-069667 ↩
  11. Lannering K, Ostman-Smith I, Mellander M. Incorporating an elevated perfusion index in the right hand enhanced screening sensitivity for critical aortic arch obstruction in newborn infants. Acta Paediatr. 2025;114(7):1570-1575. doi:10.1111/apa.17601 ↩
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  13. Stave EA, Donofrio MT, Mehta R, Park IH, Goudar SP. Fetal echocardiography enhances perinatal care for coarctation of the aorta: balancing risk of hemodynamic compromise and resource utilization. Pediatr Cardiol. Published online September 11, 2026. doi:10.1007/s00246-026-04463-1 ↩
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