Nonreceipt of newborn intramuscular vitamin K linked to doubled bleeding risk

A nationwide Swedish cohort study spanning nearly two decades has found that infants who did not receive intramuscular vitamin K at birth had significantly higher odds of bleeding during the first 6 months of life, including a nearly 3-fold increase in intracranial hemorrhage, compared with infants who received the standard prophylactic injection. The findings, published online July 13, 2026, in JAMA Pediatrics, add to a growing body of international data documenting rising parental refusal of newborn vitamin K and its downstream clinical consequences.

The study's authors, led by Eleni Simatou, MD, of Karolinska Institutet in Stockholm, concluded that continued education for parents and clinicians is needed given the persistent, and increasing, gap in protection among infants who forgo the injection.

Study design and key findings in the Swedish cohort

Researchers analyzed data from 2,020,302 live births in Sweden between 2003 and 2021, drawing on the Swedish Medical Birth Register linked to national patient, neonatal quality, and cause-of-death registers. Among this cohort, 24,089 infants (1.19%) had no documented record of intramuscular vitamin K administration at birth. After adjustment for maternal and perinatal confounders, infants without the injection had an adjusted odds ratio of 1.52 for any bleeding diagnosis and 2.91 for intracranial bleeding within 6 months, compared with infants who received intramuscular prophylaxis. Risks were even higher when restricted to the neonatal period, and a composite analysis incorporating death as a competing outcome showed similarly elevated associations. Findings were consistent across multiple sensitivity analyses, including exclusion of infants admitted to neonatal units and those with low Apgar scores.

A reversing trend after decades of low incidence

Nonreceipt of intramuscular vitamin K in Sweden fell from 1.32% in 2003 to a low of 0.66% in 2006, then climbed steadily to 1.50% by 2021, more than double the 2006 nadir. The pattern echoes prior reports of rising refusal rates in Australia, New Zealand, Great Britain, Canada, and the US, where recent hospital-based estimates have reached as high as 5.18%. Oral vitamin K, offered as an alternative when the injection is declined, was used in fewer than 10% of infants who lacked intramuscular dosing and was itself associated with higher bleeding odds than the intramuscular route, consistent with earlier reports that oral regimens depend on sustained parental adherence over 12 weeks.

Mechanism and rationale for prophylaxis

Newborns are physiologically vulnerable to vitamin K deficiency because of limited placental transfer, low concentrations in breast milk, and an immature gut microbiome that cannot yet synthesize the vitamin, factors that underlie the historical adoption of universal prophylaxis beginning in the 1960s. Sweden's own experience illustrates the stakes: a shift from intramuscular to oral-only dosing in 1986 led to a resurgence of vitamin K deficiency bleeding, prompting reinstatement of intramuscular administration as the default in 1989.

Interpreting the data

The authors note that their bleeding outcome relied on ICD-10 diagnostic codes rather than laboratory-confirmed vitamin K deficiency bleeding, likely capturing a broader group of atraumatic bleeding events and limiting direct comparison of absolute rates with prior studies, though the relative risk difference between exposure groups should remain informative. The vitamin K checkbox itself has not been formally validated within the birth register, introducing potential misclassification, and the cohort lacked data on socioeconomic status and later childhood immunization uptake, both previously linked to vitamin K refusal.

Limitations and next steps

Because the study is observational, causal inference is constrained despite extensive covariate adjustment and E-value sensitivity analysis. The authors call for further research into the specific drivers of parental refusal and its relationship to other preventive care decisions, including vaccination. Clinically, the results reinforce guidance from pediatric and midwifery organizations that counseling on intramuscular vitamin K should begin during prenatal care and be delivered transparently to support informed parental decision-making.

3 Takeaways

• Newborns without intramuscular vitamin K had an adjusted 52% higher odds of any bleeding and nearly 3-fold higher odds of intracranial hemorrhage by 6 months of age.
• Nonreceipt of intramuscular vitamin K in Sweden more than doubled between 2006 and 2021, mirroring trends reported in the US, UK, Canada, and Australia.
• Oral vitamin K, used in under 10% of infants who declined the injection, was associated with greater bleeding risk than intramuscular dosing, underscoring the importance of prenatal counseling favoring the injection.

Reference: Simatou E, Tsamantioti E, Hallström A, Stephansson O, Razaz N, Persson M, Bolk J. Vitamin K prophylaxis in newborns and bleeding in infancy. JAMA Pediatr. Published online July 13, 2026. doi:10.1001/jamapediatrics.2026.2606