According to Gram Research analysis of a 2026 JAMA cohort study, newborns who skipped the vitamin K shot had a 47% higher six-month bleeding risk than those who received it, with 288 versus 186 cases per 10,000 babies. The findings come from more than 5 million US infants.
According to Gram Research analysis of a 2026 study published in JAMA, babies who did not get the newborn vitamin K shot had a higher risk of serious bleeding than babies who received it. Researchers reviewed health records from more than 5 million US infants born between 2017 and 2025, drawn from hospitals in all 50 states. Infants who skipped the shot were about 47% more likely to have bleeding during their first six months of life. They also had more than twice the risk of bleeding inside the skull, a rare but serious problem. The share of families declining the shot rose from 3.1% in 2017 to 6.8% in 2025. Vitamin K helps blood clot, and newborns have very little of it at birth. Because this was an observational study, it shows a strong link but cannot prove the shot alone caused the difference. Still, the findings add weight to the recommendation that newborns receive this simple, routine shot.
Key Statistics
A 2026 JAMA cohort study of more than 5 million US infants found that babies who did not receive the newborn vitamin K shot had a 47% higher risk of bleeding during their first six months than babies who received it.
A 2026 JAMA cohort study reported that the share of US newborns not receiving the vitamin K shot rose from 3.1% in 2017 to 6.8% in 2025.
A 2026 JAMA cohort study found that babies who skipped the newborn vitamin K shot had about 2.4 times the risk of bleeding inside the skull, with 33 versus 13 cases per 10,000 babies.
The Quick Take
- What they studied: Researchers wanted to know how often newborns in the US are skipping the vitamin K shot given right after birth, and whether skipping it is linked to more bleeding problems in the first six months of life.
- Who participated: The study included more than 5 million babies born at full term or near full term (35 to 43 weeks) in US hospitals and health systems between 2017 and 2025. Their records came from a large national health data system covering hospitals in all 50 states.
- Key finding: Babies who did not get the vitamin K shot had about 288 bleeding cases per 10,000 babies by six months old, compared with about 186 per 10,000 among babies who got the shot. That works out to roughly 47% higher risk for the babies who skipped it. Bleeding inside the skull was also more than twice as common in that group.
- What it means for you: Parents should know that the newborn vitamin K shot is a simple way to lower the chance of a serious bleeding problem in early infancy. Parents who have questions or concerns about the shot should talk with their baby’s doctor or midwife before deciding.
The Research Details
This was a retrospective cohort study, which means researchers looked back at existing health records rather than enrolling babies and assigning them to groups. The data came from Epic Cosmos, a large database that collects electronic health records from hospitals and health systems across the United States. Researchers identified babies born between January 2017 and December 2025 and sorted them into two groups: those who received the vitamin K shot shortly after birth and those who did not.
The main measure was whether a baby had any bleeding diagnosis in the first six months of life, based on standard medical diagnosis codes. The team also tracked bleeding that happened during the birth hospital stay, bleeding after discharge, bleeding inside the skull, and deaths linked to bleeding during the birth stay. To account for differences between the two groups, such as the mother’s health, the baby’s health at birth, and where the family lived, the researchers used a statistical method called robust Poisson regression. This method estimates how much more or less likely an outcome is in one group compared with another after adjusting for those other factors.
Because the study used records from so many babies, it could detect even small differences with confidence. However, the method compares groups as they naturally occurred, so it can show that two things are linked without proving that one caused the other.
Looking at real-world health records from millions of births allows researchers to see patterns that smaller studies would miss. Bleeding from vitamin K deficiency is rare, so a very large group is needed to measure how common it is and how much the shot changes the risk. Tracking the same trend across nine years also shows whether refusal rates and bleeding rates are changing over time.
This approach is useful for spotting trends in everyday care. Since the study covers hospitals across the whole country, the results reflect how the shot is used in real clinical settings rather than in a tightly controlled trial.
The study has a major strength in its size, covering more than 5 million births across all 50 states. Using the same data source across nine years also makes it easier to compare trends fairly. The research was published in JAMA, a highly respected medical journal that uses rigorous peer review.
There are also important limits to keep in mind. Health records can contain errors or missing details, and bleeding diagnoses depend on how doctors coded them. Because families who decline the shot may differ in other ways from families who accept it, some of the difference may come from those other factors rather than the shot itself, even though the researchers adjusted for several of them.
What the Results Show
The study found that babies who did not receive the vitamin K shot had a higher chance of bleeding during their first six months. Among those who skipped the shot, bleeding occurred in 288 out of every 10,000 babies, compared with 186 out of every 10,000 babies who received it. After adjusting for other factors, babies who skipped the shot were about 47% more likely to have bleeding during this period.
The gap was even larger for bleeding inside the skull. This type of bleeding occurred in 33 out of every 10,000 babies who skipped the shot, compared with 13 out of every 10,000 who received it. After adjustments, the risk was about 2.4 times higher in the group that skipped the shot. Although intracranial bleeding is rare overall, it can cause serious and lasting harm.
The researchers also looked at deaths linked to bleeding during the birth hospital stay. These were rare, but they were more common among babies who skipped the shot, with about 2.9 deaths per 10,000 babies compared with about 1.1 per 10,000 among those who received it. After adjustments, the risk was about 2.7 times higher in the group that skipped the shot.
The number of families declining the shot also grew over the study period. The share of newborns who did not receive it rose from 3.1% in 2017 to 6.8% in 2025. Bleeding rates rose in both groups during this time, but they stayed consistently higher among babies who did not receive the shot.
Bleeding during the birth hospital stay and bleeding after discharge both showed a similar pattern, with higher rates among babies who did not receive the shot. These patterns point to the same conclusion: skipping the shot is linked to more bleeding problems across the first months of life. The consistency across different timeframes makes the overall picture more convincing.
The rise in refusals is an important public health signal. Even a small percentage increase, when applied to millions of births, means thousands more babies each year may be missing this protection.
Vitamin K shots at birth have been a standard recommendation in the US for decades, and earlier research has long linked vitamin K deficiency to serious bleeding in newborns. This study adds fresh evidence from a much larger and more recent group of babies, showing that the risk remains real in modern hospitals. It also documents a clear increase in the number of families choosing to skip the shot, which earlier studies had not tracked at this scale.
Because this was an observational study, it can show that skipping the vitamin K shot is linked to more bleeding, but it cannot prove the shot alone caused the difference. Families who decline the shot may differ in other ways, such as access to care or other health habits, and these differences can be hard to fully measure.
The study relied on electronic health records and diagnosis codes. Some bleeding events may have been missed or coded differently across hospitals. Also, the study followed babies for up to six months, so it does not show what happens to bleeding risk later in childhood.
The Bottom Line
Research shows that babies who skip the newborn vitamin K shot have a substantially higher risk of bleeding during their first six months, including a higher risk of serious bleeding inside the skull. The current evidence supports offering the shot to all newborns, since it is simple, inexpensive, and linked to meaningfully lower bleeding risk. Confidence in this recommendation is high given the large sample and consistent results, though the study’s design means it cannot fully rule out other contributing factors.
Expectant parents, new parents, pediatricians, midwives, family doctors, and hospital staff should all find this research relevant. Parents who are unsure about the shot should talk through the risks and benefits with a trusted clinician. Public health officials may also find the rising refusal rate useful when planning education efforts. People who are not expecting a baby or caring for a newborn have less direct reason to act on these findings.
The vitamin K shot works quickly. It is given within hours of birth, and it raises the baby’s vitamin K levels within the first day. The protection it provides is meant to cover the early months of life, when newborns are most vulnerable to vitamin K deficiency bleeding. Parents do not need to wait for results, since the benefit begins almost immediately after the shot is given.
Frequently Asked Questions
Does skipping the newborn vitamin K shot increase bleeding risk in babies?
Babies who skipped the shot had 288 bleeding cases per 10,000 by six months, compared with 186 per 10,000 among those who received it. That is about 47% higher risk, according to a 2026 JAMA study of over 5 million US infants.
How common is it for newborns to skip the vitamin K shot in the US?
The share of US newborns not receiving the vitamin K shot rose from 3.1% in 2017 to 6.8% in 2025. This trend, reported in a 2026 JAMA study, shows that refusals have been increasing steadily over nine years.
What is the vitamin K shot given to newborns for?
Newborns have very little vitamin K at birth, and it helps blood clot. The shot raises vitamin K levels quickly and protects against vitamin K deficiency bleeding, a rare but serious condition, during the first months of life.
Can the vitamin K shot prevent bleeding inside a baby’s skull?
A 2026 JAMA study found that babies who skipped the shot had 33 cases of intracranial bleeding per 10,000, compared with 13 per 10,000 among babies who received it. The study shows a strong link, though it is observational.
Want to Apply This Research?
- Log whether your baby received the vitamin K shot, the date and time it was given, and any questions you discussed with your provider. Record the date of your baby’s discharge and any follow-up visits in the first six months. Tracking these details in one place makes it easier to review them with your pediatrician later.
- Schedule a conversation with your baby’s doctor or midwife before the birth to discuss the vitamin K shot and any concerns you have. Add a reminder in the app to ask about the shot at your prenatal visits. If you have already decided, note your decision and the reasons behind it so you can revisit it with your provider if questions come up.
- During the first six months, check in with your baby’s pediatrician at each well-child visit and note any unusual bruising, bleeding from the navel or circumcision site, blood in stool or urine, or unexplained paleness. Record these observations in the app and share them with your provider. Keep a running log of your baby’s visits and any treatments so the full history is available at every appointment.
This article summarizes an observational study and is for general education only. It is not medical advice. The study shows a link between skipping the newborn vitamin K shot and higher bleeding risk, but it cannot prove cause and effect. Talk with your baby’s doctor, pediatrician, or midwife about whether the vitamin K shot is right for your newborn.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.