When the Lungs Are the Problem but the Brain Also Needs Watching

A study of 83 babies born with a hole in the diaphragm asks whether simple bedside monitors can spot developmental difficulties early

Babies born with congenital diaphragmatic hernia — a hole in the muscle that separates the chest from the abdomen — survive far more often than they once did, but many go on to have developmental difficulties. A new study of 83 full-term babies in China found that two bedside monitors, one measuring brain electrical activity and one measuring oxygen levels in the brain, showed no difference between babies at two days old but had clearly separated by two weeks. The finding suggests the days around surgery may be an important window for protecting the brain [1].

The Problem, and How Families Used to Face It

Congenital diaphragmatic hernia — usually shortened to CDH — happens in roughly one in every 3,000 to 5,000 babies born [2]. The diaphragm is the sheet of muscle beneath the lungs that pulls air in with every breath. When a hole forms in it before birth, organs that belong in the abdomen — the stomach, the intestines, sometimes the liver — move up into the chest and take up the space the lungs need to grow. The result is not just a hole to be closed. The lungs themselves end up small and underdeveloped, and the blood vessels inside them are stiff and narrow, which makes it hard for blood to pick up oxygen after birth [3].

For decades, this was mainly a survival story, and often a sad one. Through the 1980s and 1990s, doctors gradually learned that pushing hard on the ventilator damaged these fragile lungs, and that waiting until a baby was stable before operating worked better than rushing to surgery. They developed medicines that relax the blood vessels in the lungs, and for the sickest babies, a heart-lung bypass machine called ECMO. Together these changes lifted survival in specialist centres to around 70% to 80% [4]. Parents who once had to prepare for the worst can now, in most cases, expect to bring their baby home.

That success brought a new question into focus. Studies following CDH survivors found that somewhere between 40% and 60% had some form of neurological or developmental difficulty — most of it mild, some of it significant [5]. Researchers looking at children who had never needed ECMO found developmental differences in that group too, so the bypass machine was not the whole explanation [6]. Children were later found to have more difficulty at school [7], and specific trouble with planning, attention, and adapting to new situations in the preschool and early school years [8]. Families also report practical problems that no one warned them about — long-term feeding difficulty is one of the most common [9]. Earlier research had shown that babies who had more complications during their hospital stay tended to have more difficulties later [10], and that the length of time a baby needed a breathing tube predicted how they were doing at one year old [11].

The frustrating part is that doctors have not been able to tell, early on, which babies will struggle. Existing tools for predicting outcomes in CDH are only modestly better than a coin toss [12]. Some of this is because every baby's anatomy is different — one report describes an unexpected abnormality in a lung blood vessel hiding behind an apparently ordinary hernia [13] — and because the illness affects the whole body, not just the chest [14]. Parents are often told to "wait and see," which is honest but hard to live with.

What the Researchers Did

A team at the Children's Hospital of Soochow University in Suzhou, China, looked back at every full-term baby with CDH who had surgery at their hospital between October 2019 and February 2024 [1]. Eighty-eight babies were considered; five could not be included because they were too unstable or did not survive. That left 83 babies, all of whom had a specialised delivery in which a breathing tube was placed before the umbilical cord was cut.

The researchers then divided the babies by how they were doing developmentally, using standard assessments during the first year. Thirty-six babies met criteria for developmental impairment; 47 did not, and formed the comparison group. The two groups were remarkably similar at birth — nearly identical in gestational age, birth weight, and how long they needed a ventilator — which makes any difference between them more meaningful.

Three tools were used to watch the brain. The first, called aEEG, is a simplified brain-wave recording made through small sensors on the scalp; it was recorded for twelve hours at a time at two days, fourteen days, and twenty-eight days of age. The second, called NIRS, is a soft sensor placed on the forehead that estimates how much oxygen the brain tissue is actually getting; it ran at the same times. Neither is painful and neither requires moving the baby. The third was a structured examination at 28 days, called NBNA, in which a trained examiner scores things like how a baby settles, muscle tone, and movement. The children were then followed with developmental testing at 6 months and 1 year.

What They Found

Two things about the babies themselves stood out. Babies with more severely underdeveloped lungs — measured before birth by a ratio comparing lung size to head size — were about six times more likely to end up in the impairment group. And babies who developed high blood pressure in the lungs after their operation were roughly four times more likely to. Babies who had open surgery rather than keyhole surgery also appeared to do worse, but the researchers are careful about this one: at their hospital, surgeons chose open surgery when the hole was large or the anatomy complicated, so open surgery is probably a sign of a more severe problem rather than a cause of one.

Interestingly, several things that might seem important made no difference at all — the size of the hole in the diaphragm, the Apgar score at one minute, how long the ventilator was needed, low blood sugar, anaemia, jaundice, or infection.

The monitoring results are the striking part. At two days old, the two groups looked the same on both the brain-wave recording and the brain oxygen sensor. By fourteen days, they had clearly separated, and the difference was still there at twenty-eight days. The researchers noted that the drop in brain oxygen levels was sharpest in the first one to three days after surgery. In other words, the difference was not something the babies were born with — it appeared during their hospital stay, around the time of the operation.

When each tool was used on its own, none was especially good at identifying which babies would have difficulties. Used together, the three were much more accurate. The researchers report an accuracy figure of 0.960 on a scale where 1.0 is perfect, correctly identifying 83 in every 100 affected babies.

There is encouraging news in the follow-up. Among the babies in the impairment group, about half were developing normally across all five tested areas at 6 months, and by 1 year that had risen to roughly three-quarters. In the comparison group the figures were about seven in ten at 6 months and nine in ten at one year. Development in these babies was not fixed at birth — many caught up substantially over the first year.

What This Means for Families

If your baby has CDH, the practical takeaway is not alarming. It is that developmental follow-up should be arranged as a normal part of care, not as a response to something going wrong — particularly if your baby's lungs were significantly underdeveloped before birth or if they had high blood pressure in the lungs after surgery. Asking your team to write a follow-up plan into the discharge summary is a reasonable and useful request.

It is also worth understanding the limits of this study honestly. It looked at 83 babies at a single hospital, all of whom had a specialised type of delivery that most hospitals do not use, and babies who were the sickest — those who were unstable or who died — were not included. The impressive accuracy figure comes with an important catch: one of the three tests used to make the prediction was also one of the tests used to decide which group a baby belonged to, which makes the result look better than it truly is. No brain scans were done. So this is a promising signal from one centre, not a finished tool ready to give a family a number.

What is genuinely useful is the timing. Two groups of babies who looked identical at two days old had visibly diverged by two weeks. That points attention toward the days surrounding surgery as a period when the brain may be vulnerable, and it suggests that watching brain oxygen levels then — not only the heart and lungs — may be worth doing.

What Researchers Are Working On Next

The next step is to test this in more hospitals, with more babies, and with continuous rather than occasional monitoring around the time of surgery, alongside brain imaging to see what is actually happening. Researchers also want to know whether responding to a falling brain oxygen level — by adjusting blood pressure, blood counts, or ventilator settings — actually changes how children develop, which this study cannot answer. And because difficulties in CDH survivors often only become apparent at school age [7], [8], following children for a single year is only the beginning.

References

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  2. Ersöz Köse E, Yalçınkaya İ. Congenital diaphragmatic hernia. Turk Gogus Kalp Damar Cerrahisi Derg. 2024;32(Suppl 1):89–97. doi:10.5606/tgkdc.dergisi.2024.25705 ↩
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