High blood pressure in babies born early: what doctors give, what happens later, and what families can ask for

Two 2025 studies — one on how newborn units treat high blood pressure, one following 2459 children to age 18 — seen from a family's point of view

Babies born too early sometimes develop high blood pressure in newborn intensive care, and doctors treat it — but no guideline says which medicine to use. Two 2025 studies fill in opposite ends of the picture: one found a large American hospital reached for the same drug about 61% of the time, out of local habit rather than evidence, and the other found that 25% of children born preterm had lasting high blood pressure, against 16% of those born at term.

Why high blood pressure in a premature baby is a real thing

Almost one in ten babies in the United States is born prematurely, meaning before 37 weeks of pregnancy, and around 95% of them now survive [1]. Surviving is not the end of the story. A small number of these babies develop high blood pressure — called hypertension — during their stay in the neonatal intensive care unit, or NICU. One large study across 24 newborn units — the Assessment of Worldwide Acute Kidney Injury Epidemiology in Neonates study, known as AWAKEN — estimated that this affects roughly 2 in every 100 NICU admissions [2], and specialists generally believe the true figure is higher, because the condition is easy to miss [3]. If severe high blood pressure is left untreated in a baby, it can damage blood vessels, the brain, the eyes and the heart. So it is not something a NICU team can ignore.

Why a baby's blood pressure is hard to define at all

In an adult, "normal" blood pressure is a single familiar number. In a newborn, there is no such number. What counts as high depends on how many weeks pregnant the mother was at delivery, how many days or weeks old the baby is now, and how much the baby weighs — and all three change constantly. Doctors therefore work from percentile charts, the same idea as the growth charts used to plot a child's height: a reading above the 95th percentile means the baby's blood pressure is higher than 95 out of 100 comparable babies. The charts most commonly used come from a 2012 review of blood pressure in infancy [4] and, for older babies, from a national report published back in 1987 [5]. These charts do not cover every age and size combination: in the first of the two 2025 studies, the researchers could not calculate a percentile at all for a large share of the babies in their own records.

How this problem used to be faced

For decades, the causes of high blood pressure in newborns were better understood than the treatment. Doctors learned to look for two things in particular. The first is a complication of the umbilical catheter — a fine tube placed in the vessels of the umbilical cord to give medicines and take blood samples in the sickest newborns — which can occasionally cause a small clot that reduces blood flow to a kidney and pushes blood pressure up. The second is chronic lung disease of prematurity, also called bronchopulmonary dysplasia, which is often accompanied by raised blood pressure that can appear weeks after the breathing problems themselves have settled and may persist after the baby goes home [6][7]. Knowing the causes, however, never translated into knowing the cure. No clinical trial has ever compared blood-pressure medicines head to head in premature babies. The largest earlier survey, covering 348 newborn units in the United States between 1997 and 2013, simply recorded which drugs were given, and found that a medicine called hydralazine was used most often [8].

The first study: what one hospital actually does

Perez and colleagues looked back through twelve and a half years of pharmacy and medical records, from July 2010 to December 2022, at the University of Alabama at Birmingham Hospital in Birmingham, Alabama [9]. They searched for babies born before 37 weeks who were still under a year old when they went home and who had received a blood-pressure-lowering medicine while in hospital. They found 134 hospital stays involving 120 babies. Their question was very practical and, surprisingly, had never been answered: in what order do doctors actually reach for these drugs? Which one is tried first? Which one is used instead if the first is stopped? Which one is added alongside another?

The answer was that one drug dominated at every stage. Propranolol — a beta-blocker, a type of medicine that slows the heart and relaxes the force of each beat — was the first choice in about 61% of cases, roughly five times more often than the next most common drug, captopril. It was also the most common second choice and the most common add-on, although so few babies ever needed a second drug or a combination (six and twelve hospital stays respectively) that those findings were too uncertain to be conclusive. Five of the fourteen possible medicines were never given at all, two of them simply because the hospital pharmacy does not stock them.

The authors are careful about what this does and does not mean. It does not mean propranolol is the right answer. It means nobody knows what the right answer is. There are no professional guidelines for treating high blood pressure in premature babies, no trial evidence on which drug works better or is safer, and practice varies enormously between hospitals — the earlier national survey found the opposite drug in first place [8]. What a premature baby with high blood pressure receives depends largely on which hospital they happen to be in.

The second study: what happens over the following eighteen years

Makker, Kuiper and colleagues followed 2459 children from the Boston Birth Cohort, a long-running research group of mothers and babies recruited at Boston Medical Center in Boston, Massachusetts [10]. The children were born between 1999 and 2014, and their blood pressure was measured at ordinary check-ups with their paediatrician — 19,736 readings in total — up to the age of 18. The typical child was followed for 8 years.

The researchers sorted the children into five groups: born at term with no NICU stay (the comparison group), born at term but admitted to the NICU, born early but never admitted to the NICU, born early with a NICU stay but no major complication, and born early with a NICU stay and at least one major complication — infection, chronic lung disease, a serious bowel condition called necrotising enterocolitis, or bleeding into the brain. They then counted how many children in each group went on to develop persistent hypertension, defined as high blood pressure recorded at three or more separate visits.

The result was a staircase. One in four children born preterm (25.2%) developed persistent hypertension, compared with about one in six of those born at term (15.8%). After accounting for the mother's health, education, smoking and stress, and the child's sex and birth size, children born early who had spent time in the NICU without a major complication had a 62% higher risk, and those who had a major complication an 87% higher risk. Measured another way, which also takes into account when the high blood pressure appeared, the last group was more than twice as likely to develop it. Preterm children also carried a slightly higher blood pressure percentile right through childhood and adolescence — a shift in the whole pattern rather than the odd high reading. One finding is easy to overlook: babies born at term who nonetheless needed the NICU also carried extra risk.

Why these two studies belong side by side

Neither paper mentions the other. They were published about five months apart and address the same children from opposite ends of their lives. The first describes an acute problem being treated at the cot side with no evidence base at all [9]. The second describes where those same children end up, with blood pressure still measurably higher a decade or more later [10]. This matches what national registry studies of adults have long suggested — that being born early raises the risk of high blood pressure well into adult life [11] — and fits the broader idea that cardiovascular health begins to be shaped before birth and in the first weeks after it [12]. The blood pressure a doctor treats in a NICU cot and the blood pressure a paediatrician measures at age 12 belong to the same story, and at neither end is the evidence good enough.

What this means for your family

None of this should be alarming, and it is worth saying clearly what it does not mean. It does not mean your child will develop high blood pressure; three out of four children born preterm in the Boston study did not. It does not mean the medicine your baby was given was the wrong one. What it does mean is that a history of prematurity, and especially a NICU stay with complications, is a lifelong reason to have blood pressure measured rather than assumed.

Helpfully, the guidance already exists. The American Academy of Pediatrics recommends that all children have their blood pressure checked once a year from the age of 3 — but that children under 3 who were born prematurely or had any NICU stay should have it checked at every single visit to a clinician, starting in infancy [13]. That recommendation is often not followed in practice, so it is entirely reasonable to ask for it by name. It is also worth asking, before discharge, why a particular medicine was chosen, what the plan is for stopping it, and what should be written in the discharge letter for the family doctor. High blood pressure that begins in childhood is linked to heart and circulatory problems later on [14], and it is far easier to act on when someone is looking for it.

What researchers are working on next

The authors of the first study set out a three-step plan: record systematically how these babies are treated now, then work out which treatment is best, then write guidelines everyone can follow [9]. Step one is under way and needs repeating at other hospitals before step two can begin. The other open questions are whether treating high blood pressure in the NICU changes what happens years later, and whether finding it early in childhood makes a difference to adult heart health [10]. Nobody has yet followed the same children from their NICU medication chart to their teenage readings.

In summary

One 2025 study showed that in a large American newborn unit, the choice of blood-pressure medicine for premature babies is made by local habit because there is nothing better to go on. The other showed that children born early — particularly those seriously unwell as newborns — carry higher blood pressure into childhood and adolescence. Together they describe one connected problem currently managed as two unrelated ones. For families the takeaway is simple: ask for a blood pressure check at your child's paediatric visits, and make sure prematurity is written into the record that follows them.

References

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  2. Kraut EJ, Boohaker LJ, Askenazi DJ, Fletcher J, Kent AL. Incidence of neonatal hypertension from a large multicenter study [Assessment of Worldwide Acute Kidney Injury Epidemiology in Neonates—AWAKEN]. Pediatr Res. 2018;84(2):279–89. doi:10.1038/s41390-018-0018-8 ↩
  3. Sharma D, Pandita A, Shastri S. Neonatal hypertension: an underdiagnosed condition, a review article. Curr Hypertens Rev. 2014;10(4):205–12. doi:10.2174/1573402111666150213153002 ↩
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