High blood pressure in newborns, called neonatal hypertension, is uncommon but has a wide range of causes. It affects roughly 0.3% of healthy newborns and between 0.7% and 3.2% of babies in the neonatal intensive care unit. Kidney problems are the single most frequent cause, but heart defects, hormonal conditions, lung disease, and even certain NICU procedures can all raise a newborn’s blood pressure.
Kidney Problems Are the Leading Cause
The kidneys play a central role in regulating blood pressure at every age, and in newborns they are the most common source of the problem. Blood clots in the renal artery (the vessel supplying the kidney) can trigger a surge in renin, a hormone the kidneys release to raise blood pressure when they sense reduced blood flow. Even a partial blockage tricks the kidney into behaving as though the body needs higher pressure, and the result is sustained hypertension.
Other kidney-related causes include structural abnormalities a baby is born with, such as kidneys that didn’t develop fully, cystic kidney disease, or obstruction of urine flow. Because so many neonatal hypertension cases trace back to the kidneys, an ultrasound of the kidneys and their blood vessels is typically one of the first tests doctors order when a newborn’s blood pressure is elevated.
Heart and Blood Vessel Defects
Coarctation of the aorta is one of the most important cardiovascular causes. In this condition, a section of the aorta (the body’s largest artery) is abnormally narrow, forcing the heart to pump harder to push blood past the narrowed segment. Blood pressure measured in the arms can be significantly higher than in the legs, which is a classic clue. Coarctation often occurs alongside other heart defects, including holes between heart chambers, valve abnormalities, or underdevelopment of the left side of the heart.
Even after surgical repair in infancy, long-term high blood pressure remains a recognized complication of coarctation. That means babies who had successful surgery still need blood pressure monitoring as they grow.
Umbilical Catheter Complications
Sick or premature newborns sometimes need an umbilical artery catheter, a thin tube placed through the blood vessel in the umbilical cord stump to deliver fluids, nutrition, or medications and to draw blood. While often necessary, this catheter can damage the vessel wall or promote blood clot formation. If a clot travels to the aorta or the arteries feeding the kidneys, it can trigger the same renin-driven blood pressure spike described above. This is one of the more well-documented procedural causes of neonatal hypertension and was first reported in the New England Journal of Medicine decades ago.
Hormonal and Genetic Conditions
Congenital adrenal hyperplasia (CAH) is an inherited condition in which the adrenal glands can’t produce cortisol normally, most often because of a missing enzyme. The body compensates by overproducing other adrenal hormones, including androgens and signals that affect salt and water balance. Children with CAH have a higher rate of hypertension than the general population, and the salt-wasting form of the disease carries an even greater risk than milder types.
Treatment for CAH itself can contribute to the problem. Babies with CAH receive replacement hormones, and if the doses tip slightly too high, the medications can raise blood pressure on their own. Balancing these medications is one of the ongoing challenges of managing the condition.
Other, rarer endocrine causes include tumors or abnormalities of the adrenal glands that produce excess amounts of hormones involved in blood pressure regulation.
Chronic Lung Disease
Bronchopulmonary dysplasia (BPD) is a chronic lung condition that develops in premature babies who needed oxygen support or ventilation after birth. Infants with BPD have significantly higher rates of high blood pressure than the general newborn population, though the exact mechanism is still being studied. Possible explanations include changes in how blood flows through damaged lung tissue, the effects of prolonged oxygen therapy, and the stress of chronic illness on the cardiovascular system. Because the link is well established, premature babies diagnosed with BPD are routinely screened for elevated blood pressure.
Medications Used in the NICU
Several medications commonly given to very premature infants can raise blood pressure as a side effect. Corticosteroids, frequently used to treat chronic lung disease, are among the best-studied culprits. In one study of very preterm infants receiving dexamethasone (a potent corticosteroid), every single baby experienced a rise in systolic blood pressure. The median peak increase was 24 mmHg, with some infants seeing jumps as high as 49 mmHg. The effect peaked around day four of treatment and persisted for at least 48 hours after the medication was stopped. In one case, the blood pressure rise was severe enough to affect the brain.
Other medications that can contribute include drugs used to support heart function and certain pain medications. NICU teams monitor blood pressure closely whenever these treatments are in use.
How High Blood Pressure Shows Up in Newborns
One of the challenges with neonatal hypertension is that babies can’t tell you how they feel, and the symptoms are easy to confuse with many other newborn illnesses. Affected infants may show feeding difficulties, weak sucking, irritability, vomiting, episodes where breathing pauses, rapid breathing, or changes in muscle tone (either unusually floppy or unusually stiff). Some babies drop their oxygen levels. Because none of these signs are unique to high blood pressure, doctors typically discover the problem through routine monitoring or while investigating another concern.
How Blood Pressure Is Measured in Newborns
Measuring blood pressure accurately in a tiny infant is harder than it sounds. There are two main approaches. The gold standard is a direct arterial line, a thin catheter placed inside an artery that gives continuous, real-time readings. It’s very accurate but carries risks including blood clots, infection, and bleeding. Less critically ill babies are monitored with an oscillometric cuff, the infant-sized version of the familiar arm cuff, which is safer but less precise and only gives intermittent snapshots.
Normal blood pressure in a newborn depends on gestational age, birth weight, and postnatal age, so there’s no single number that defines “high.” Doctors compare a baby’s readings against reference charts specific to these factors. A reading consistently above the 95th percentile for the baby’s age and size is generally considered hypertensive.
What Happens After a Diagnosis
When sustained high blood pressure is confirmed, doctors work to identify the underlying cause because treatment depends almost entirely on what’s driving it. A clot may need to be addressed directly. A heart defect like coarctation may require surgery. A hormonal imbalance calls for careful medication adjustment. If a NICU medication is responsible, the team weighs the risks of the blood pressure elevation against the benefits of the drug and may adjust the dose or switch to an alternative.
Many cases of neonatal hypertension resolve once the underlying cause is treated or the triggering medication is stopped. Some babies, particularly those with structural heart or kidney problems, need ongoing monitoring well into childhood because their risk of recurrence remains higher than average.