Infants Not Receiving Vitamin K at Birth May Be More Likely to Experience Bleeding

Newborns who did not receive vitamin K at birth may have an elevated risk for bleeding, according to the findings of a new retrospective cohort study of more than 5 million infants published in JAMA. The findings come as the number of parental refusals of the standard intramuscular vitamin K injection for newborns continues to grow.

The study researchers identified 5,240,780 infants, of whom 234,825 (4.5%) did not receive vitamin K, and 99,828 (1.9%) had infant bleeding. The researchers found that there was a 47% increased risk of bleeding during the first six months of life among infants who did not receive the vitamin K injection (adjusted relative risk 1.47.) When stratified by vitamin K administration, the number of infants per 10,000 births with bleeding increased across the study period from 225.3 to 394 among those who did not receive vitamin K and from 136.6 to 221.8 among those who did.

“These findings highlight the critical need for clinical and policy efforts to prevent neonatal morbidity and mortality due to vitamin K deficiency,” the authors wrote.

The United States initiated universal newborn intramuscular vitamin K prophylaxis in 1961; previous research has shown it has been effective in preventing vitamin K deficiency bleeding (VKDB) since then. Normal blood clotting requires vitamin K, and prophylaxis is necessary for newborns, who are born with physiologically low vitamin K stores. VKDB can result in intracranial and gastrointestinal hemorrhage, leading to neurological disability and mortality, though occurrence is rare. The American Academy of Pediatrics recommends vitamin K for all newborns.

The study included infants in Epic Systems Corporation’s Cosmos research platform born between Jan. 1, 2017, and Dec. 31, 2025. Bleeding events included intraventricular hemorrhage, intracranial hemorrhage, newborn hemorrhage (including gastrointestinal hemorrhage), and VKDB. The researchers specifically looked at bleeding from birth through six months of age, with additional analysis bleeding during the birth hospitalization and after the birth hospitalization and before six months of age.

The researchers determined that one additional infant with bleeding in the first six months would occur among 114 newborns not receiving vitamin K at birth. In addition, newborns who did not receive vitamin K had higher risks of specific types of bleeding, including intracranial, and mortality with concurrent bleeding during the birth hospitalization.

In an accompanying editorial, nutritional and pediatric experts wrote, “Every clinician would be distraught to learn an infant experienced a bleeding event and to hear a parent report, ‘if only I had known the risk.’ Armed with the information from this study, pediatric clinicians can now more confidently communicate the protection provided by intramuscular vitamin K prophylaxis and use these figures to encourage a comprehensive U.S. public health effort encompassing directed messaging, public health surveillance and new therapeutics.”