A large U.S. study has found that more newborns are missing the routine vitamin K injection, alongside an increase in bleeding diagnoses during the first six months of life.
The research, published in JAMA on November 5, 2026, examined more than 5.2 million infants born between 2017 and 2025 at hospitals and health systems across all 50 states.
The researchers found that the share of babies without documented vitamin K administration rose from 3.1 per cent in 2017 to 6.8 per cent in 2025.
Table of Contents
What the vitamin K study found
Vitamin K is essential for normal blood clotting, but newborns naturally have low stores because only small amounts cross the placenta and newborn intestines do not yet produce enough of the vitamin.
Among infants who did not receive the injection, bleeding by six months increased from 225.3 cases per 10,000 births in 2017 to 394.0 cases per 10,000 births in 2025.
Bleeding also increased among infants who received vitamin K, rising from 136.6 to 221.8 cases per 10,000 births over the same period.
The study was observational, meaning it identified an association rather than proving that declining vitamin K receipt alone caused every increase.
The researchers said the findings nevertheless raise concern because infants who did not receive vitamin K had a substantially higher risk of bleeding than those who received the preventive dose.
The study included infants born at 35 to 43 weeks of gestation and used electronic health records from the Epic Cosmos research platform.
That design allowed researchers to examine a very large population, but it also means the results depend on the accuracy and completeness of medical records.
Why vitamin K deficiency bleeding can be dangerous
Vitamin K deficiency bleeding, commonly called VKDB, can occur when an infant does not have enough vitamin K to form blood clots.
Bleeding may occur from the umbilical cord or digestive tract, but it can also happen inside the brain, where it may not be immediately visible.
The U.S. Centers for Disease Control and Prevention says most babies with VKDB have no warning signs before a serious bleeding event.
Possible symptoms include unusual bruising, pale skin, blood in vomit or stool, black tarry stool, extreme sleepiness, irritability, seizures or repeated vomiting.
Late VKDB can develop from one week to six months after birth, with brain bleeding reported in 30 to 60 per cent of late-onset cases, according to the CDC.
The CDC says infants who do not receive the shot are 81 times more likely to develop late VKDB than infants who receive it, although the condition remains uncommon overall when newborns routinely receive prophylaxis.
What Canadian parents should know
The new study was conducted in the United States and does not establish that vitamin K refusal or newborn bleeding has increased at the same rate in Canada.
Canadian guidance, however, also recommends routine vitamin K for newborns.
The Canadian Paediatric Society and the College of Family Physicians of Canada recommend one intramuscular dose shortly after birth, generally within the first six hours after stabilization.
The recommended dose is 0.5 milligrams for infants weighing 1,500 grams or less and 1.0 milligram for infants weighing more than 1,500 grams.
The Canadian Paediatric Society says oral vitamin K can be considered when parents decline the injection, but it is less effective and requires doses at birth, two to four weeks and six to eight weeks.
Parents who choose the oral option are advised that their baby remains at higher risk of late VKDB, particularly if follow-up doses are missed.
Why some parents decline the injection
Researchers and hospitals have reported concerns about injection pain, ingredients, possible side effects and preference for oral or “natural” alternatives among parents who decline newborn vitamin K.
The CDC says the injection has been studied extensively and that later research did not confirm an early-1990s concern about a possible connection between vitamin K and childhood cancer.
The Canadian Paediatric Society describes the injection as the preferred and most effective prevention method, while recommending steps such as holding the baby and allowing sucking during the injection to reduce discomfort.
What happens next
The study adds to a growing body of research examining whether declining acceptance of routine newborn preventive care is contributing to the return of conditions that had become rare.
Researchers are likely to continue monitoring whether the rise in recorded bleeding reflects a sustained national pattern, changes in diagnosis or documentation, or a combination of factors.
For families expecting a baby, Canadian guidance is to discuss vitamin K before delivery and ask the health-care team about the timing, dose, pain-reduction measures and alternatives if the injection is declined.
Frequently Asked Questions
What is vitamin K deficiency bleeding?
Vitamin K deficiency bleeding is a condition in which a baby cannot form blood clots properly because the body does not have enough vitamin K. It can cause bleeding inside the intestines, brain or other parts of the body.
When can vitamin K deficiency bleeding happen?
It can occur from birth through the first six months of life. Late-onset cases most commonly occur between two and eight weeks after birth.
Does the vitamin K shot prevent all newborn bleeding?
No, but it is highly effective at preventing vitamin K deficiency bleeding. Other causes of bleeding can still occur, and urgent medical assessment is needed for concerning symptoms.
Is the vitamin K injection recommended in Canada?
Yes. The Canadian Paediatric Society recommends a single intramuscular dose for all newborns, preferably within six hours after birth following initial stabilization.
What if parents decline the vitamin K injection?
Canadian guidance allows an oral regimen as an alternative, but it is less effective and requires multiple doses. Parents should discuss the increased risk of late bleeding with their health-care provider.
Fact-Checked: Key figures and medical guidance were checked against the 2026 JAMA study, the Canadian Paediatric Society and CDC primary information.
Disclaimer: This article is for general information and is not a substitute for urgent medical advice or individualized guidance from a qualified health-care professional.