Vitamin K Prophylaxis in Newborns and Bleeding in Infancy

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 6 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 nonreceipt 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 nonreceipt 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 hemorrhages. 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.