Soft Bones in Tiny Babies: What Four New Studies Say About Preventing Them

Recent research from Saudi Arabia, Turkey and China, plus a review of every trial ever done, on why premature babies' bones need help and what actually works

Babies build most of their skeleton in the last weeks of pregnancy. A baby born very early misses that window, and their bones can end up softer and more fragile than they should be — a condition doctors call metabolic bone disease of prematurity. Four studies published in 2025 and 2026 looked at how often this happens, why it happens, and what genuinely prevents it.

Why bones are the last thing to finish

Growing a skeleton takes a great deal of calcium and phosphorus, and a pregnancy delivers most of it late. In the final stretch of gestation, the placenta pumps these minerals across at a rate no feeding method can easily match afterwards. A baby born at 25 or 26 weeks simply never receives that final delivery. Instead, the job of mineralising a skeleton falls to the neonatal unit, at a moment when the baby may be too unwell to feed, is being fed through a vein rather than a stomach, and is deliberately being left as undisturbed as possible.

Each of those necessary things works against bone. Nutrition given through a drip can only carry so much calcium and phosphorus before the two minerals form crystals in the bag, which puts a hard ceiling on how much can be delivered. Some medicines premature babies genuinely need — water tablets for the lungs, steroids for breathing — also pull calcium out of the body or slow the cells that build bone. And bones need to be pushed and pulled to grow strong: in the womb a baby kicks against the uterine wall constantly, and in an incubator that stimulus largely disappears.

How doctors used to find this, and why that changed

For a long time this problem was found on X-rays, when a baby's bones looked thin or a rib or leg bone had quietly broken. The trouble is that an X-ray only shows the change once roughly a third of the bone's mineral has already gone [1] — by which point the window for preventing it has closed.

So attention moved to blood tests. The main one is an enzyme called alkaline phosphatase, which rises when the cells that build bone are working hard without enough raw material arriving. Doctors also measure phosphate and calcium, and check how much phosphate the kidneys are holding on to — if the kidneys are hoarding it, the body is genuinely short rather than losing it [2]. Paediatric societies published recommendations for how much calcium and vitamin D premature babies should get, and how to screen [3]. What never got agreed was the number at which a baby should be said to have the condition. Different hospitals draw the line in different places, and that turns out to matter enormously.

The four new studies

The first followed 487 babies born before 28 weeks and weighing under 1,000 grams at King Abdulaziz Medical City in Riyadh, Saudi Arabia, between 2017 and 2024. That unit has run a structured bone health programme since 2017, meaning every eligible baby gets the same blood tests at the same age and the same nutritional review. Using a hormone called parathyroid hormone as its marker, it found the condition in 41.5% of babies [4].

The second followed 413 babies born at 32 weeks or under, or weighing 1,500 grams or under, at a hospital in Bursa, Turkey, between 2020 and 2024. Using a stricter three-part blood test rule, it found the condition in 19.8% [5].

The third, from a hospital in Shijiazhuang, China, followed 657 babies born between 26 and nearly 37 weeks, with a smaller group of 63 who had blood and urine sampled repeatedly to track the hormones that control minerals. It found the condition in 11.3% [6].

The fourth was different in kind: a review that gathered every study ever published on treating or preventing the condition — 18 studies from ten countries, covering 1,577 babies — and combined their results to ask what actually works [7].

The first thing to notice is that the three hospitals report very different rates — 41.5%, 19.8%, 11.3% — largely because they used different definitions, not because their babies were that different. This is the single biggest unresolved problem in the field: a baby diagnosed with this condition in one hospital might not have been in another, and the reverse is equally true.

What the studies agreed on

Despite using different definitions, all three hospitals pointed to the same causes, which is reassuring.

Time on intravenous nutrition was the strongest common thread. In Riyadh, babies fed through a drip for more than 28 days had significantly higher odds of the condition. In Bursa, every extra day added measurable risk, with a rough tipping point at about 19 or 20 days [5]. In Shijiazhuang, long drip feeding was again on the list [6]. This is not an argument against intravenous nutrition, which keeps babies alive — it is an argument for getting babies onto milk as early as they can safely tolerate it.

Certain medicines added risk. In Riyadh, water tablets given for more than two weeks roughly doubled the odds, and steroids raised them too [4]. These medicines are given for good reasons; knowing they carry a bone cost simply means watching those babies more closely.

Vitamin D timing mattered a great deal. In the Chinese study, babies who did not start extra vitamin D until after two weeks of age had roughly five times the odds of developing the condition — the single strongest changeable factor in that cohort [6]. The mothers there were also widely low in vitamin D themselves, so many babies started life with little reserve.

The blood picture lined up too. Affected babies had higher alkaline phosphatase and, where measured, much higher parathyroid hormone — the hormone the body releases when it senses a calcium shortage and starts drawing on the skeleton to make up the difference [8]. The Riyadh study found this hormone flagged babies with X-ray changes reasonably well, which supports adding it to routine screening.

One uncomfortable finding

The Riyadh researchers checked whether babies who developed the condition had been given less calcium and phosphorus than the others. They had not. Intakes were essentially identical between the two groups, both before and after screening, and both sat within recommended ranges [4] [9] [10]. In other words, topping up the minerals once the blood tests turn abnormal does not appear to undo what has already happened. Prevention has to start earlier than detection.

What actually works

This is where the review of all the trials is most useful [7]. Two approaches came out with real support.

Giving minerals early, before there is any sign of a problem. Across the trials, babies given preventive calcium and phosphorus from the first days of life were substantially less likely to develop the condition — roughly half as likely overall, and in the highest-risk groups the reduction was larger still. Put in everyday terms, treating about five high-risk babies this way prevents one case. The strongest individual results came from a Chinese study of early calcium and phosphorus supplements [11] and from an Australian unit that reformulated its intravenous nutrition to carry more calcium and a different form of phosphate, after which severe cases disappeared entirely [12]. Vitamin D strategies, whether higher doses or doses adjusted to each baby's blood level, also helped [13].

Gently moving the baby's arms and legs. This is the finding most parents find surprising. Several trials tested short sessions — five to sixteen minutes a day, five days a week, for four to eight weeks — in which someone gently bends and straightens the baby's joints, sometimes with light pressure along the limb. Bone strength measured by ultrasound improved substantially, weight gain improved, and no study reported a single adverse event; pain scores confirmed the babies tolerated it well. Twice a day worked better than once [14], and one trial found parents delivering the movements did as well as therapists [15]. Researchers rated this evidence less certain than the nutrition findings, because you cannot hide from a nurse whether a baby is being exercised and the trials were small. But it is safe, free, and makes physiological sense.

What this means for your baby

If your baby is very premature, expect a blood test around four weeks looking at bone markers, and possibly a repeat. A raised alkaline phosphatase result is common and is not by itself an emergency — it is a signal for the team to look at nutrition. Extra calcium, phosphate or vitamin D may be added, and roughly a third of the most affected babies in the Riyadh study went home still taking mineral supplements, against about one in six of the others [4].

Fractures do happen, but are much less common than the word "fragile" suggests. In the Riyadh unit, which X-rayed babies routinely, fractures occurred in under 2% of all babies studied. In the Turkish unit, which only X-rayed when something looked wrong, the recorded rate among affected babies was higher — partly because that approach misses quiet fractures in the smallest, stillest babies while catching them in the ones well enough to protest [5]. Neither number is the "true" one; they measure different things.

Babies with this condition also tended to grow more slowly and stay in hospital longer — in Riyadh, a median of 97 days against 78 [4] [16]. Whether the bone problem causes the longer stay or simply travels with the sickest babies is not something these studies can answer.

If you want to help, ask the team whether gentle limb movements are appropriate for your baby yet, and whether you could be shown how to do them. Ask when they plan to move from drip feeding to milk. Ask whether your baby is on vitamin D. These are exactly the levers the research points to, and they are ones a parent can reasonably be part of.

What researchers are working on next

Three things. First, and most importantly, agreeing on a definition — several 2026 reviews are now arguing that the field cannot make progress until the diagnostic threshold is settled, because every incidence figure and every trial result currently depends on a locally chosen number [17] [18]. Second, following children for longer. Pooled scan data suggest bone density remains somewhat lower into young adulthood after preterm birth [19], while long-term follow-up in the trials review found no difference in lifetime fracture rates between people born preterm and those born at term; a study now tracking bone health from infancy into middle age should help resolve this [20]. Third, better detection. One 2026 study trained a computer model to read wrist X-rays and identify the condition, which could give doctors a consistent measure that does not depend on who is looking at the film [21].

For now, the practical message is encouraging. This is a condition of timing, not of fate: the things that make it more likely — long spells on intravenous feeding, late vitamin D, lying very still — are things neonatal teams can influence, and the evidence says acting early works better than reacting late.

References

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