When a Baby's Heart Problem Reaches the Gut

What three recent studies tell families about bowel illness in newborns with serious heart defects — how common it is, who is most at risk, and what it means for feeding

Babies born with serious heart defects can develop a dangerous bowel illness called necrotizing enterocolitis, which most people associate with very premature infants. Three recent studies show that in full-term babies with critical heart disease it is uncommon — roughly two to seven in every hundred — but serious when it does happen, and that it is driven mainly by poor blood flow to the intestine rather than by an immature gut.

If your baby has a heart defect that needs surgery in the first weeks of life, you may have heard the medical team mention this illness, or noticed that they seem hesitant about starting milk feeds. That hesitation has a history, and until recently it rested on surprisingly thin numbers. Between late 2024 and mid-2026, three research teams published work that finally puts figures to the risk: a review that pooled every published study on the subject [1], a study from Shanghai comparing babies with heart defects to premature babies with the same bowel illness [2], and a four-year study from Istanbul that followed 780 full-term newborns with critical heart disease [3].

What this illness is, and why it used to be thought of as a premature baby's disease

Necrotizing enterocolitis — clinicians usually shorten it to NEC — is an illness in which part of the intestinal wall becomes inflamed, loses its blood supply, and can begin to die. Babies stop tolerating milk, their abdomen swells, and in the most severe cases the bowel wall can perforate. It has been recognised for decades as one of the most feared complications in newborn intensive care [4].

For most of that history, the babies affected were extremely premature. Their intestines had not finished developing, their immune defences were immature, and the bacteria colonising their gut were unusual. That picture shaped everything: the way the illness is graded, the way it is prevented, and the way it is studied.

Then, around the year 2000, doctors began reporting the same illness in full-term babies whose only apparent vulnerability was a heart defect [5]. The staging system used to describe severity — developed in 1978 for premature infants — was applied to these babies too, even though nobody had checked whether it fitted them [6]. Slowly, an explanation emerged. In certain heart defects, blood that should flow forward into the body instead drains backward into the lungs between heartbeats, robbing the intestine of the steady supply it needs. Doctors could actually see this pattern on ultrasound of the abdominal aorta, and babies who showed it were more likely to become ill [7]. The defects at highest risk turned out to be those in which survival depends on a fetal blood vessel, the ductus arteriosus, staying open [8].

This left teams in an awkward position. Feeding a baby increases the intestine's demand for blood — in a healthy newborn the gut takes only a small share of the heart's output at rest, but far more after a feed. If the heart cannot meet that demand, feeding might tip a fragile intestine over the edge. Many units responded by keeping babies with duct-dependent heart defects on intravenous nutrition until after surgery. But that approach has real costs: central lines carry infection risk, and babies who never practise feeding by mouth take much longer to learn afterward. When one hospital introduced a careful, gradual feeding plan rather than no feeding at all, the illness became less common, not more [9]. Other studies found no evidence that feeding before surgery caused harm [10], [11]. What no one could say was how big the risk being avoided actually was.

What the three studies did, and what they found

The Istanbul study is the most straightforward. Researchers reviewed every full-term baby with critical heart disease cared for in their heart intensive care unit over four years — 780 infants — and counted how many developed the bowel illness [3]. Eighteen did: 2.3%, or about one in every 43 babies. Almost all of them (16 of 18) had a duct-dependent heart defect. Most became ill in the first week of life, at a median age of seven days. Fourteen recovered with medical treatment — bowel rest, a feeding tube to decompress the stomach, intravenous nutrition, and antibiotics — while four needed abdominal surgery.

The study also identified which babies were most vulnerable. Four things independently raised the risk: having a heart with only one functioning pumping chamber (nearly six times the risk), needing a breathing machine (about five times), weighing less than 2.5 kilograms at birth (about four times), and being born before 38 weeks (about four times). That last finding is worth pausing on, because every baby in this study was full term. Even within "full term," the earliest babies were the most vulnerable.

The pooled review put those numbers in a wider context. Drawing together 86 studies and nearly 68,000 babies, it found that among the studies judged most reliable, about 7 in every 100 infants with congenital heart disease developed the illness [1]. Among premature babies with heart defects, the figure was higher — about 13 in 100. Surgery was needed in fewer than 1 in 100 full-term babies. Interestingly, the less carefully conducted studies reported lower rates, which suggests that where doctors are not looking systematically, cases are being missed. Recent work on standardising the way the diagnosis is made in babies with heart disease points the same way [12].

The Shanghai study answered a different question: are these two groups of babies really the same? It compared 60 infants who developed the illness alongside a heart defect with 120 infants who developed it without one [2]. The differences were stark. The babies with heart defects were born much closer to their due date (about 38.7 weeks on average, compared with 30.7) and were more than twice as heavy at birth. They were far more likely to have been in circulatory shock and to have needed a breathing machine and strong medications to support blood pressure. The premature babies, by contrast, more often had infections and other complications of prematurity. In short: same illness on paper, two different roads to it.

What this means for your baby

The most useful takeaway is that the risk, while real, is small for most babies. A rate of around 2 to 7 in 100 means that the large majority of newborns with serious heart defects will never develop this illness. And the risk is not spread evenly — it concentrates in babies with duct-dependent circulation, single-ventricle hearts, those on breathing machines, and those born smaller or earlier.

Because of this, many teams no longer withhold milk from every baby awaiting heart surgery. Instead they make feeding decisions individually, based on how well the baby's circulation is working on that particular day — blood pressure, how well the hands and feet are perfusing, how the abdomen looks and sounds. If your team pauses feeds, it is usually a response to something specific they are seeing, not a permanent verdict.

Breast milk matters here. Babies with complex heart defects who received human milk before surgery had a lower risk of developing the illness [13], and a clinical trial has tested an exclusive human milk diet in babies with single-ventricle hearts [14]. If you are expressing milk, you are contributing something the medical team cannot substitute.

There are two periods when teams watch most closely: the first week of life, before surgery, and the first three days after the operation. In the Istanbul study, nearly two-thirds of the cases that occurred after surgery appeared within 72 hours of it [3]. This is why nurses check abdominal size, listen for bowel sounds, and measure what remains in the stomach so frequently in those windows. It can feel like excessive fussing. It is the opposite.

One more practical detail: in babies with heart defects, the injured part of the bowel is often the colon rather than the small intestine, which is the reverse of the pattern in premature babies [15]. Doctors caring for cardiac newborns know to look in a different place on the X-ray. If your team seems to be examining things that were not mentioned to friends whose babies were born early, this is one reason why.

Honesty about outcomes matters too. In the Istanbul study, half the babies who developed the illness did not survive, compared with fewer than 8% of those who did not — a pattern seen in larger multi-hospital data as well [16]. Those numbers reflect the fact that this illness tends to occur in the sickest infants, whose hearts were already struggling. They are not a prediction for any individual child, and they are the reason the watching is so careful.

What researchers are working on next

Three directions are active. The first is agreeing on a definition of this illness that actually fits babies with heart disease, so that hospitals count the same thing and can compare results [12]. The second is early warning: sensors placed on the abdomen that measure oxygen levels in the tissue beneath, and ultrasound of the gut's blood vessels, may one day signal trouble before symptoms appear. The third is nutrition — building the evidence needed to say confidently which feeding approach is safest for which heart defect, rather than borrowing rules written for premature babies [17].

If you take one thing from this research, let it be this: the intestine in these babies is usually reporting on the heart. When teams respond to an abdominal concern by re-examining your baby's circulation, they are following the evidence.

References

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  2. Balati K, Xu Z, Zhu L, Gong X. Clinical characterization of necrotizing enterocolitis in neonates with or without congenital heart disease: a case–control study. Italian Journal of Pediatrics. 2025;51(1):93. doi:10.1186/s13052-025-01928-6 ↩
  3. Kangel D, Recep E, Çevlik B, et al. Necrotizing Enterocolitis in Term Neonates with Critical Congenital Heart Disease: Associated Risk Factors and Clinical Outcomes. Journal of Cardiovascular Development and Disease. 2026;13(7):329. doi:10.3390/jcdd13070329 ↩
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