Does Keeping Premature Babies on Breast Milk Longer Help Their Brains Grow?

A Plain-Language Look at New Brain Scan and Movement Findings from a Study of Very Premature Infants

Why Nutrition and Brain Development Both Matter So Much for Premature Babies

A new study looked at whether keeping extremely premature babies on an all-human-milk diet — their own mother's milk or donor milk, with no cow's-milk-based formula or booster — for a few extra weeks helps their brains grow and mature. The researchers compared brain scans and movement assessments between babies who stayed on this diet longer and those who switched to cow's-milk-based products earlier, and found the two groups looked almost identical on most measures. One movement-quality score was a little better in the longer-human-milk group at one checkpoint, but that advantage disappeared by the next check three months later — so while the study raises no concerns, it does not yet prove an added brain benefit either.

Babies born very early — many months before their due date — still have a lot of brain development left to do. In the womb, the last few months of pregnancy are when the brain's surface starts folding into its familiar wrinkled shape, when nerve pathways get their protective coating, and when a structure called the cerebellum (the part of the brain involved in coordinating movement) grows especially fast. When a baby is born very prematurely, all of that has to keep happening in a hospital nursery instead of in the womb, and doctors have long wondered whether what a baby is fed during that time might affect how well the brain manages this catch-up growth.

For a long time, doctors favored human milk for very premature babies mainly to protect the gut, not the brain. A well-known 2010 study found that premature babies fed only human milk — with no cow's-milk-based formula or booster added — had a lower rate of a serious bowel problem called necrotizing enterocolitis, or NEC for short (a condition where part of the intestine becomes inflamed and can be seriously damaged) [1]. That finding helped make all-human-milk diets common practice in newborn intensive care units. Once doctors saw that human milk protected the gut, researchers started asking whether it might help the brain too. Brain-scan studies found that babies who received more breast milk early on showed differences in how brain regions were connected to each other [2], and in how the brain's outer layer, the cortex, matured [3]. Longer-term studies followed some of these children to age seven and found links between how much breast milk they received as newborns and their thinking skills years later [4], a pattern seen again in a separate, larger group of children [5]. None of these studies could prove that breast milk itself caused the difference, but together they raised a specific question this new study addresses: would giving it for even longer give babies' brains an extra boost too?

Why does this matter so much? Being born very early is common — roughly one in ten babies worldwide arrives before their due date [6] — and the earliest, smallest babies face a real risk of brain injury and long-term challenges with thinking, movement, or behavior, even with today's advanced newborn intensive care [7], with higher rates of these difficulties confirmed in children followed after extremely preterm birth [8]. Doctors now see preterm brain injury as a mix of direct injury — like bleeding or reduced blood flow — and gradual disruption of normal brain growth [9], a view that has shifted research toward supporting healthy brain maturation, not just preventing injury [10]. Brain scans done around a baby's original due date are a fairly reliable early clue to how a child's development might unfold [11], which is why researchers use brain scans, like the ones in this study, to test whether a change in care — such as a feeding approach — might make a meaningful difference.

The Study: Comparing Two Feeding Approaches with Brain Scans and Movement Checks

This particular study is part of a bigger project called NEOVASC (the name refers to exclusive human milk feeding and early signs of blood vessel aging in premature babies) that compared babies who stayed on an all-human-milk diet longer against those who switched to cow's-milk-based products earlier [12]. The overall NEOVASC study included babies from four hospitals across Austria, but the brain-scan and movement part of the research described here was done at just one of those hospitals, the Medical University of Innsbruck, Austria [13].

Fifty-four babies took part in this brain-focused portion of the study. All were born very early — most between about 27 and 30 weeks of pregnancy (a full-term pregnancy is about 40 weeks) — and weighed under 1,250 grams (about 2 pounds, 12 ounces) at birth. Twenty-eight babies were assigned to keep receiving only human milk — their own mother's milk or, when that wasn't available, donor milk from a milk bank, boosted with a human-milk-based booster (called a fortifier, which adds extra calories, protein, and minerals) — all the way until they reached the equivalent of 36 weeks of pregnancy age (doctors call this postmenstrual age, or PMA — basically, how far along the pregnancy would be if it were still ongoing). The other twenty-six babies followed the usual feeding order too — mother's milk first, then donor milk, then formula if needed — but switched over to a cow's-milk-based booster or formula earlier, at 32 weeks PMA.

To see whether the extra weeks of an all-human-milk diet made a difference, the research team used magnetic resonance imaging (MRI, a brain scan that uses magnets and radio waves rather than X-rays) around the time each baby reached full-term-equivalent age. They also used a special type of scan called diffusion tensor imaging (DTI), which tracks how water molecules move through brain tissue — a way of checking how well the brain's internal wiring, the nerve pathways that carry signals between brain regions, is developing. Alongside the scans, trained assessors watched video recordings of each baby's spontaneous movements and scored their quality using two standard tools: the General Movement Optimality Score (GMOS), used at three early checkpoints, and the Motor Optimality Score (MOS), a related but separate scoring tool used at one later checkpoint, three months after the last GMOS check.

What the Researchers Found: Mostly No Difference, and One Signal That Faded

On the brain scans, the two groups of babies looked remarkably similar. Rates of brain bleeding (called intraventricular hemorrhage, or IVH — bleeding into the fluid-filled spaces inside the brain, a well-known risk for very premature babies) were not significantly different between the two groups, and neither was any other category of brain injury the researchers checked for. Measurements of brain size and growth were also essentially the same in both groups. On the detailed wiring scans (DTI), there were two small differences that looked statistically meaningful at first — both, oddly, suggesting slightly less mature wiring in the babies who stayed on human milk longer — but once the researchers accounted for the fact that more babies in that group had been smaller than expected for their age at birth (a factor known to affect brain wiring on its own), those differences stopped looking meaningful. In plain terms: those two findings were probably explained by which babies happened to be smaller at birth, not by which diet they were on. No brain scan measure suggested that the longer human-milk diet caused any harm.

The one finding that did stand out, at least at first, involved the movement-quality score. At an early checkpoint (34 weeks) there was no difference between the groups, and by 36 weeks the human-milk group was scoring a bit higher, though not by a difference large enough to rule out chance. By 40 weeks, the human-milk group's scores were meaningfully higher than the other group's. That looked promising — until the babies were checked again three months later, at 52 weeks, using the related but slightly different movement tool. At that later check, the two groups scored almost exactly the same. This one promising early result did not hold up when the babies were checked again later, which is a common pattern when researchers test many different things at once: some differences will look meaningful just by chance, and the honest conclusion is that this one, so far, has not been confirmed.

What This Means for Families of Premature Babies

If your baby was born very prematurely, this study is genuinely good news in one sense: it found no red flags. Extending an all-human-milk diet to 36 weeks did not show any sign of causing more brain injury or slower brain growth than switching to cow's-milk-based products earlier. At the same time, the study did not clearly prove an extra brain benefit either — the one promising early sign did not hold up at the later check. The researchers themselves are upfront about this [13]: they describe their findings as an early, exploratory look rather than a final answer, noting the study was small — only 54 babies — which makes it hard to detect anything but a fairly large effect, if one exists.

It's also worth knowing that both groups in this study received mostly human milk for most of their hospital stay — the difference being tested was really about four extra weeks of an all-human-milk diet, not human milk versus formula from day one. The well-established reason doctors already favor human milk for very premature babies is its protection against necrotizing enterocolitis, that serious bowel problem mentioned earlier, and nothing here changes that. Families can feel reassured that their care team's feeding choices are already backed by solid evidence for gut and infection protection, and that this new study, while not yet proving an extra brain benefit, gives no reason for concern either.

What Researchers Are Working On Next

The scientists behind this research say the natural next step is a bigger study — one with enough babies to detect smaller effects with more confidence, and one that tracks more detailed information about exactly how much human milk each baby received, rather than just which feeding group they were assigned to. They also note that the larger project this study is part of — which followed babies at hospitals across Austria, not just the one hospital in this brain-focused analysis — is planning to check in on these children again at preschool age, looking at their thinking, language, and movement skills over the longer term. That future follow-up will be a much stronger test of whether extending an all-human-milk diet actually changes how these children develop. For now, families of very premature babies can take comfort in knowing that the feeding approaches their care teams already use are grounded in solid evidence, with this study adding one more careful, honest data point to an ongoing conversation.

References

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