Bleeding episodes among infants aged six months or younger in Sweden doubled between 2003 and 2021, a concerning trend apparently driven by more parents declining vitamin K shots for their newborns, according to an analysis of 2m infants published in JAMA Paediatrics.
The authors, all affiliated with the Stockholm-based Karolinska Institutet, said that the babies with no record of intramuscular vitamin K administration were 50% more likely to have bleeding compared with babies who received the shot, reports CIDRAP News.
Intracranial bleeding was even higher in babies who didn’t receive the shot, at more than 300%, and they said 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 Paediatrics 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.
Babies born at home less likely to get the 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 between 2018 and 2021 did not have documentation of receiving the prophylaxis.
The authors speculate this extremely high rate might be due to under-reporting 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 than intramuscular administration.
Study details
Vitamin K Prophylaxis in Newborns and Bleeding in Infancy
Eleni Simatou, Eleni Tsamantioti, Anna Hallström et al.
Published in JAMA Paediatrics on 13 July 2026
Key Points
Question Is the rate of non-receipt of intramuscular vitamin K prophylaxis among newborns increasing, and is non-receipt associated with an increased risk of bleeding in infancy?
Findings In this cohort study including 2m infants in Sweden, non-receipt of newborn intramuscular vitamin K prophylaxis doubled over time, and a significantly higher proportion of the infants lacking the prophylaxis had bleeding episodes during infancy.
Meaning These results suggest the need for continued education to parents and health care practitioners about the importance of newborn prophylactic vitamin K.
Abstract
Importance
Vitamin K deficiency bleeding in infants is a rare but potentially life-threatening condition that is effectively prevented by newborn intramuscular vitamin K prophylaxis. Despite this, there are reports of increasing parental refusal of vitamin K prophylaxis globally.
Objective
To evaluate temporal trends of prophylactic newborn vitamin K administration and its association with bleeding diagnoses during infancy.
Design, Setting, and Participants
This was a nationwide cohort study of births between January 1, 2003, and December 31, 2021, followed up until six months of age. The study setting was in Sweden and included all live-born infants born at 35 or more weeks’ gestation during the study period. Data analysis was performed from June 1 to December 19, 2025.
Exposure
The exposure was non-receipt of intramuscular vitamin K administration at birth.
Main Outcomes and Measures
The primary outcome was a bleeding diagnosis within the first 6 months of life. Data from the Swedish Medical Birth Register was linked to multiple Swedish national registers. Logistic regression was used to estimate adjusted odds ratios (aORs) with 95% CIs.
Results
Among 2 020 302 live births, 24 089 infants (mean [SD] gestational age, 40.0 [1.6] weeks; 12 472 male [51.8%]) had no record of intramuscular vitamin K administration at birth. The rate of non-receipt decreased during the first study years from 1.32% (1242 of 94 214 newborns) in 2003 to 0.66% (667 of 100 429 newborns) in 2006, and then gradually increased and more than doubled to 1.50% (1619 of 107 915 newborns) in 2021. Infants without intramuscular vitamin K administration had 1.54-fold higher odds (aOR, 1.52; 95% CI,1.27-1.81) of bleeding and 3.18-fold higher odds (aOR, 2.91; 95% CI, 2.13-3.96) of an intracranial bleeding episode during infancy, compared with infants with intramuscular vitamin K.
Conclusions and Relevance
This cohort study shows that the number of infants in Sweden who do not receive intramuscular vitamin K administration at birth to prevent bleeding episodes continues to be low but is increasing, and these infants have a significantly higher associated risk of bleeding episodes, including intracranial haemorrhages. These findings suggest the importance of intramuscular vitamin K administration in the newborn period to prevent bleeding episodes and the need for continued education of parents and caregivers on its significance.
JAMA Paediatrics article – Vitamin K Prophylaxis in Newborns and Bleeding in Infancy (Open access)
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Evidence of vitamin K benefits for heart health — 23-year Australia study
Direct oral blood-thinners tied to fewer brain bleeds – Finnish analysis
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