For most of his 10 years as a neonatologist, Dr. Timmy Ho encountered one or two parents per week who didn’t want their newborns to receive a vitamin K injection, a standard step to prevent bleeding.
Recently, in just one week, he saw three or four per day — numbers, he said, that were becoming more common.
One of the babies suffered a type of bleeding in the brain that vitamin K could have prevented, said Dr. Ho, who practices in Boston. He had never seen that before.
Vitamin K plays a crucial role in blood clotting but doesn’t pass to the baby through the placenta effectively, and there isn’t much of it in breast milk. Infants are deficient in it until they can eat solid foods. This can lead to bleeding, from minor oozing from the umbilical cord to potentially life-threatening gastrointestinal or brain hemorrhages.
One injection immediately after birth is very effective at fixing the deficiency, and it has been routinely administered in the United States for more than 60 years.
Now, the shot appears to have been swept up in broader anti-vaccine sentiment, even though it isn’t a vaccine.
More generally, providers said, some parents are refusing a range of medical precautions for their newborns, including an antibody injection against respiratory syncytial virus, or R.S.V., and an antibiotic ointment to prevent eye infections that babies can contract if their mother has gonorrhea.
But several providers said they tried especially hard to persuade parents to accept the vitamin K shot.
“It comes from good intentions — it’s people who are scared of doing something wrong to their child,” Dr. Ho said. “The trouble is, by not doing something, you are doing something wrong to your child.”
The vast majority of parents still accept the vitamin K shot. But a paper last month, based on electronic medical records, found the number of U.S. infants not receiving the injection jumped to over 5 percent in 2024 from under 3 percent in 2017.
Those numbers don’t reveal why the babies didn’t receive the injection. But several providers said the rhetoric and policies of President Trump and Health Secretary Robert F. Kennedy Jr. seemed to have turbocharged the trend.
Dr. Cliff O’Callahan, the chair of pediatrics at Middlesex Health in Connecticut, has long had patients whose parents opposed vaccines. But, he said, only a handful declined vitamin K until recently. Now, not only are more parents hesitant, he said, but fewer can be convinced.
A few years ago, he estimated, he persuaded up to 75 percent of reluctant parents; now, it’s less than 50 percent.
Some parents encounter misinformation about vitamin K injections linked to outdated research. In the early 1990s, a small study suggested they might be linked to leukemia, but larger studies since then have found no link.
Providers said that wasn’t what most hesitant parents cited, though. Rather, most say they consider the shot unnatural or unnecessary. Others want oral vitamin K, but there is no oral version for babies approved by the Food and Drug Administration, and what is available online has to be given repeatedly over weeks, compared with a single shot.
Some parents have also expressed concerns about benzyl alcohol, a preservative in vitamin K injections, said Dr. Emilie Sebesta, the medical director of the Mother/Baby Unit at the University of New Mexico Hospital. In the 1980s, researchers found risks to premature babies from large doses of the ingredient, but there is no evidence of harm from the small amount in the vitamin K shot, according to Dr. Sebesta and the Centers for Disease Control and Prevention.
Babies can bleed for a number of reasons, especially if they are premature, but vitamin K deficiency is a significant and preventable cause. While bleeding from lack of vitamin K is uncommon — affecting an estimated 0.25 percent to 1.7 percent of untreated infants in the first week of life, and an additional fraction of a percent in the first six months — the injection nearly eliminates that risk.
The difficulty is that, aside from prematurity increasing risk, doctors can’t predict who will suffer, so the American Academy of Pediatrics has recommended the injection for all newborns since the 1960s.
While some forms of bleeding are minor, brain bleeds can be devastating. “Once it happens, you can’t control it,” said Karen Skific, a nurse practitioner in a neonatal intensive care unit in Mobile, Ala. Providers can only try to treat symptoms and keep the baby stable until the bleeding stops.
Death rates vary depending on the site and timing of bleeding from vitamin K deficiency, but some studies put them around 20 percent. Many survivors have brain damage, causing developmental delays or disabilities like cerebral palsy.
Unlike vaccines, vitamin K is sometimes administered routinely in hospital nurseries under the general treatment consent form that new parents sign. But more parents are proactively saying they don’t want it, said Ms. Skific, who has worked in neonatal intensive care units for more than 20 years.
The numbers are small, perhaps 5 percent, she said, “but it used to be never.”
Maggie Astor covers the intersection of health and politics for The Times.
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