Bleeding episodes among infants of 6 months of age or younger in Sweden doubled from 2003 through 2021.
This concerning trend seems driven by more Swedish parents declining vitamin K shots for their newborns, according to an analysis of 2 million infants published today in JAMA Pediatrics.
Swedish babies with no record of intramuscular vitamin K administration were 50% more likely to have bleeding compared with babies who received the shot. Intracranial bleeding was even higher in babies who didn’t receive the shot, at more than 300%.
The study’s authors, all affiliated with the Stockholm-based Karolinska Institutet, argue their findings show an ongoing need for clinicians to discuss with parents how vitamin K prophylaxis is vital in preventing potentially deadly bleeding among infants.
Vitamin K helps newborns form blood clots
Newborns have low levels of vitamin K because only small amounts of it cross the placenta. The vitamin is essential for the body to form blood clots to stop bleeding, so it’s standard practice to administer an intramuscular shot of it into a baby’s thigh muscle within six hours of birth.
The American Academy of Pediatrics has recommended that newborns receive vitamin K shots since 1961 to prevent Vitamin K Deficiency Bleeding (VKDB). The intervention profoundly reduces the risk of this rare but life-threatening condition that can cause uncontrolled internal bleeding, including in the brain.
Refusal of the prophylaxis is an international issue, including in the United States: An analysis of electronic health records published in JAMA in January found that the rate of refusal by US parents grew from 2.92% in 2017 to 5.18% in 2024. In contrast, the Swedish researchers found that in 2021, the final year of their analysis, just 1.5% of babies went without a vitamin K shot.
Breast milk has low levels of vitamin K, so babies who are exclusively breastfed remain at risk of VKDB until they begin eating solid foods.
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Babies born at home are less likely to get a vitamin K shot
The growing refusal of vitamin K shots for newborns seems to be driven by similar fears that undermine trust in vaccines. As CIDRAP News recently reported, suspicions of the pharmaceutical industry and traditional medicine are among the reasons parents reject this well-studied intervention.
The Swedish study did not compare vaccination rates with vitamin K uptake, but researchers did find a correlation with home births. Nearly two out of every three Swedish infants born at home from 2018 through 2021 did not have documentation of receiving the prophylaxis.
The authors speculate this extremely high rate might be due to underreporting in non-hospital settings but said this “aligns with previous reports that parental refusal of vitamin K is more common at home births.”
The study also observed a higher frequency of oral vitamin K administration, which is less effective at preventing VKBD compared to intramuscular administration.
Sarah Boden is a health care journalist. She has won numerous awards for her health care coverage, including being named the 2025 Keystone Media Freelancer of the Year. Follow Sarah on X @Sarah_Boden
A version of this article was originally posted at the University of Minnesota and is reposted here. Any reposting should credit both the GLP and original article. Find the University of Minnesota on X @UMNews
