Researchers say a rise in parents opting not to give their newborns vitamin K shots is associated with an increase in infant bleeding.
According to a study published in JAMA and conducted by a team of researchers, the percentage of newborns not receiving a vitamin K shot more than doubled between 2017 and 2025. In 2017, 3.1% of newborns did not receive a vitamin K shot. By 2025, that figure had risen to 6.8%.
The study found the bleeding rate within the first six months of life was 288 per 10,000 infants who did not receive vitamin K, compared with 185.9 per 10,000 among infants who received it.
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Intracranial bleeding, or bleeding in the brain, was also significantly more common among infants who did not receive vitamin K. After researchers adjusted for other factors, the risk was about 2.4 times higher than among infants who received the shot.
Bleeding rates also rose among infants who received vitamin K between 2017 and 2025. Researchers said the reasons for the overall increase are unclear and could include changes in how bleeding is identified or differences in the health of mothers and infants.
The researchers noted that the study was observational, meaning it found an association between not receiving vitamin K and increased bleeding risk but did not definitively establish cause and effect.
"Routine intramuscular vitamin K administration has been highly effective at preventing vitamin K deficiency bleeding in newborns for decades," said Heather H. Burris, one of the study's co-authors. "Our study is the first to document a nationwide decline in administration paired with increases in bleeding risks. Our findings underscore the importance of continued education and awareness, so families understand the serious, preventable bleeding risks for infants who do not receive vitamin K at birth."
Vitamin K has long been given to newborns to help prevent dangerous bleeding. Newborns generally have low levels of vitamin K because only small amounts cross the placenta during pregnancy. Breast milk also contains low levels of vitamin K, and infants may not get enough from their diets until they begin eating other foods.
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The Centers for Disease Control and Prevention recommends that newborns receive a vitamin K shot shortly after birth.
"The findings reinforce the longstanding recommendation that newborns receive the one-time intramuscular vitamin K injection shortly after birth and highlight the need to better understand why its use is declining," said lead author Kristan Scott.
