A growing number of parents in the United States are refusing vitamin K injections for their newborns, a trend that pediatric experts warn could put thousands of babies at risk of life-threatening bleeding disorders.

A new study published on December 8 in JAMA analyzed medical records of more than five million infants born across 403 hospitals between 2017 and 2024. Researchers found that roughly 4% of babies — about 200,000 infants — did not receive the vitamin K shot, a standard preventive treatment given shortly after birth. The refusal rate rose steadily from under 3% in 2017 to more than 5% by 2024, with the steepest increases recorded in the years following the COVID-19 pandemic.

“The increase is not surprising, but the degree to which it did increase did catch me off guard,” said study author Dr. Kristan Scott, a neonatologist at Children’s Hospital of Philadelphia, in an interview with NBC News.

Unlike vaccines, vitamin K injections are a supplement designed to help newborns’ blood clot. Babies are born with naturally low vitamin K levels, putting them at high risk for vitamin K deficiency bleeding (VKDB). According to the U.S. Centers for Disease Control and Prevention, infants who do not receive the shot are more than 80 times more likely to develop dangerous bleeding.

Such bleeding can appear anytime within the first six months of life, and may present as bruising, internal bleeding, or — in the most severe cases — brain hemorrhage that can cause permanent disability or death. “We are creating a population of newborns who are at risk of bleeding,” Scott said. “Bleeding into the brain is what we really worry about… essentially a stroke. That can ultimately cause death.”

Doctors say the surge in refusals is likely fueled by online misinformation and confusion about the purpose of the injection. “Parents are equating vitamin K injections to vaccines,” said Dr. Tiffany McKee-Garrett, a neonatologist at Texas Children’s Hospital, who was not involved in the study. Health experts stress that the vitamin K shot is not a vaccine and has been a universally recommended standard of care for decades.

Some countries do offer oral vitamin K, but U.S. physicians caution that oral formulations are less reliable and often require multiple doses. The injection given at birth is considered the most effective option, offering complete protection with a single shot.

Vitamin K deficiency is entirely preventable, and experts say the rise in refusals is deeply concerning. “We shouldn’t be seeing it at all,” said Dr. Ivan Hand, a neonatologist at NYC Health + Hospitals in Brooklyn. He warned that as refusals increase, hospitals are likely to see more cases of severe bleeding — a condition many clinicians have rarely encountered because the preventive shot has been so successful.

“These treatments have been so effective that people don’t understand the consequences,” Hand said. “They have never seen babies with severe bleeding, so they think it doesn’t exist. But you don’t see it because we are treating these kids.”