Sometimes the Safest Choice Is to Do Less: What a Major Study Learned About Platelet Transfusions for Premature Babies

How the two-year results of the PlaNeT-2 trial reshaped one common intensive-care decision

A large international study followed premature babies who had low platelet counts and found that giving platelet transfusions more freely did not help them and actually caused harm that lasted into early childhood. Babies given transfusions at a more generous threshold were more likely to have died or to have a developmental problem by age two than babies given them only when their counts fell much lower. The clear lesson: for these infants, a more cautious, "wait-and-watch" approach is safer.

Why platelets, and why this question matters

Platelets are tiny cells in the blood that help it clot and stop bleeding. Babies born many weeks early are fragile, and one of the things doctors worry about most is bleeding in the brain, which can cause lasting harm. Premature babies often have low platelet counts, and for many years the instinct in newborn intensive care was to top those platelets up with a transfusion before any bleeding started—just to be safe. It felt like the protective thing to do [1].

The trouble was that this instinct had almost never been properly tested. The one older study that looked at the question used very different conditions, and it did not show that extra platelets prevented brain bleeding [2]. Meanwhile, doctors noticed something uncomfortable in their records: babies who received more platelet transfusions often seemed to do worse, not better [3]. That was only an association, not proof—sicker babies naturally need more of everything—but it was enough to make researchers want a real answer.

It helps to understand why so many premature babies have low platelet counts in the first place. A baby born many weeks early is still building the systems that make and regulate blood cells, and platelet production can simply lag behind need. On top of that, the very conditions that land a baby in intensive care—infections, bowel problems such as necrotising enterocolitis, and the general stress of being born too soon—tend to drive platelet counts down further. So a low count is extremely common, and it often appears precisely in the babies who are already the sickest. That overlap is part of what made the old records so hard to interpret: it was never clear whether the transfusions themselves were causing harm, or whether the babies who needed them were simply more fragile to begin with. Only a randomised trial, where chance alone decides who gets what, could untangle the two.

How the study worked

To get that answer, researchers ran a carefully designed trial called PlaNeT-2. Between 2011 and 2017, they enrolled 660 babies born before 34 weeks of pregnancy who had low platelet counts and were not actively bleeding, across 43 newborn intensive care units in the United Kingdom, the Netherlands and Ireland [4]. Each baby was randomly assigned—essentially by the flip of a coin—to one of two approaches. In the "higher threshold" group, a baby got a platelet transfusion whenever the count dropped below 50 (in the units doctors use). In the "lower threshold" group, transfusion waited until the count dropped below 25. Random assignment matters because it makes the two groups alike in every other way, so any difference in how the babies do can be credited to the transfusion strategy itself rather than to how sick they were to begin with.

The first results, published in 2019, were surprising: babies in the more generous, higher-threshold group had more deaths and serious bleeding in the first month, not fewer [1]. But a single month is a short window in the life of a premature baby. Many families and doctors reasonably wondered whether the more generous approach might still pay off later. So the researchers did something important—they followed the same children to age two to find out [4].

What they found at two years

The follow-up reached an impressive 92% of the children, which makes the findings trustworthy [4]. The early warning did not fade with time—it grew clearer. By age two, half of the children (50%) in the higher-threshold group had either died or were living with a significant developmental problem, such as cerebral palsy or a delay in learning and movement. In the lower-threshold group, that figure was 39% [4].

One helpful way to picture the size of this difference: for roughly every nine babies cared for with the more cautious approach instead of the generous one, one child was spared death or a serious developmental problem [4]. That is a large benefit from a change that involves doing less rather than more. And importantly, the more cautious approach did not simply keep frailer babies alive only to face disability—the children who survived in that group were no more likely to have problems. They simply did better overall.

There was also a lung finding. Babies in the generous-transfusion group were more likely, two years later, to still need extra oxygen or breathing support [4]. Long-term breathing problems in babies born early are themselves linked to later difficulties with development [5], so this fit the overall picture of harm from the more generous approach.

It is also worth knowing what the original worry was, because the study turned it on its head. The whole reason doctors gave platelets early was to prevent serious bleeding in the brain. Yet in the first month, the babies given the more generous transfusions actually had slightly more of these brain bleeds, not fewer [1]. In other words, the treatment meant to prevent the very thing everyone feared seemed to make it a little more likely. This is a powerful reminder that a number on a lab report is not the same as the problem itself, and that "fixing" the number does not always make the baby safer.

Why might extra platelets cause harm?

Scientists cannot yet say for certain, but they have good leads. It turns out platelets are not just simple "plugs" that stop bleeding—they are active cells that influence inflammation and the immune system [6]. The platelets used in transfusions come from adult donors, and an adult's platelets may behave differently inside the delicate, still-developing body of a premature baby [7]. Researchers suspect that giving more of them may stir up inflammation or worsen bleeding in the brain, both of which can affect a child's long-term development [8]. This is still being studied, but it helps explain a result that at first seems backwards.

What this means for families and what comes next

If your baby is in newborn intensive care with a low platelet count and the team chooses to wait rather than transfuse right away, this can feel worrying—it is natural to assume that more treatment means more protection. But in this particular situation, the best evidence we have shows the opposite. Choosing not to transfuse a baby who is not bleeding, when the platelet count is above the lower threshold, is an active, careful decision made to protect your child, grounded in one of the largest studies ever done on the question [4]. It is always reasonable to ask your team to explain their reasoning.

It can also help to know what a result like this does and does not say. The study looked at babies who were not actively bleeding and whose platelet counts had fallen into a moderate range. It does not mean platelet transfusions are never useful—when a baby is bleeding seriously, or when the count falls very low, transfusion remains an important treatment, and those situations call for individual judgement by the care team. What the study settled is narrower but important: routinely topping up platelets in a stable, non-bleeding premature baby, just because a number looks low, does more harm than good. That distinction is why the care team will weigh your baby's whole situation rather than react to a single lab value.

This shift toward "less is more" is happening across newborn care. Studies of red-blood-cell transfusions have reached similar conclusions—that giving blood more freely does not improve children's later development [9], [10]. Researchers are now working to understand exactly why extra platelets cause harm, how best to care for babies who are actively bleeding (a different situation this study did not cover), and whether even more cautious thresholds might be safe. For now, the message from this trial is both reassuring and clear: for premature babies who are not bleeding, holding back on platelet transfusions is the safer path [4].

References

  1. Curley A, Stanworth SJ, Willoughby K, et al. Randomized trial of platelet-transfusion thresholds in neonates. N Engl J Med. 2019;380(3):242–251. doi:10.1056/NEJMoa1807320 ↩
  2. Andrew M, Vegh P, Caco C, et al. A randomized, controlled trial of platelet transfusions in thrombocytopenic premature infants. J Pediatr. 1993;123(2):285–291. doi:10.1016/s0022-3476(05)81705-681705-6) ↩
  3. Baer VL, Lambert DK, Henry E, et al. Do platelet transfusions in the NICU adversely affect survival? J Perinatol. 2007;27(12):790–796. doi:10.1038/sj.jp.7211833 ↩
  4. Moore CM, D'Amore A, Fustolo-Gunnink S, et al; for the PlaNeT2 MATISSE Collaborators. Two-year outcomes following a randomised platelet transfusion trial in preterm infants. Arch Dis Child Fetal Neonatal Ed. 2023;108(5):452–457. doi:10.1136/archdischild-2022-324915 ↩
  5. DeMauro SB, Jensen EA, Bann CM, et al. Home oxygen and 2-year outcomes of preterm infants with bronchopulmonary dysplasia. Pediatrics. 2019;143(5):e20182956. doi:10.1542/peds.2018-2956 ↩
  6. McFadyen JD, Kaplan ZS. Platelets are not just for clots. Transfus Med Rev. 2015;29(2):110–119. doi:10.1016/j.tmrv.2014.11.006 ↩
  7. Ferrer-Marin F, Chavda C, Lampa M, et al. Effects of in vitro adult platelet transfusions on neonatal hemostasis. J Thromb Haemost. 2011;9(5):1020–1028. doi:10.1111/j.1538-7836.2011.04233.x ↩
  8. Maitre NL, Marshall DD, Price WA, et al. Neurodevelopmental outcome of infants with unilateral or bilateral periventricular hemorrhagic infarction. Pediatrics. 2009;124(6):e1153–e1160. doi:10.1542/peds.2009-0953 ↩
  9. Kirpalani H, Bell EF, Hintz SR, et al. Higher or lower hemoglobin transfusion thresholds for preterm infants. N Engl J Med. 2020;383(27):2639–2651. doi:10.1056/NEJMoa2020248 ↩
  10. Franz AR, Engel C, Bassler D, et al. Effects of liberal vs restrictive transfusion thresholds on survival and neurocognitive outcomes in extremely low-birth-weight infants: the ETTNO randomized clinical trial. JAMA. 2020;324(6):560–570. doi:10.1001/jama.2020.10690 ↩