The baby was born full-term and healthy, but now, just a few weeks later, lay limp and unresponsive, barely breathing.

“The baby was diagnosed with bleeding in the brain,” said Dr. Ivana Culic, a neonatologist at Boston Children’s Hospital and medical director of the special care nursery at Beverly Hospital. “Babies that suffer intracranial bleeding — or bleeding in the brain — unfortunately suffer damage that can be lifelong.”

The child survived. Medical privacy rules bar Culic from revealing more details of this recent Boston-area case she saw, but she could say this: The parents of the baby had refused the standard shot of Vitamin K that would almost certainly have prevented that bleed.

“Personally, it is actually really hard to take care of any infant or baby that is sick,” she said. “But when you realize that a severe illness was completely preventable, that is something that is really hard for everyone to comprehend and deal with in our field.”

It’s standard medical care: Newborn babies get a shot of Vitamin K. It helps their blood clot, and prevents potentially dangerous bleeds. But a few new parents decline the shots for their babies, and their numbers seem to be rising — an apparent trend that’s deeply troubling to doctors from Nashville to New Zealand.

American health authorities do not track Vitamin K refusals. But in recent years, anecdotal reports from hospitals and the CDC have described clusters of several babies who had brain bleeds and whose parents had declined the Vitamin K shot.

Dr. Robert Sidonio Jr., now of Emory University, helped document such a cluster in Nashville in 2013: five babies with brain bleeds over six months. It turned out, he said, that while traditionally over 99 percent of babies receive Vitamin K shots, more than 3 percent of Nashville parents were declining the shots — and in nearby communities with private birthing centers, nearly 30 percent were declining.

“And this is in a relatively medium-sized city that tends to be relatively conservative,” he said, “so that was sort of shocking to us, that there were that many parents declining it. It was quite shocking to the CDC as well.”

What Are They Thinking?

So why would a parent decline a treatment that’s been standard for more than 50 years and proven to prevent a serious risk?

Dr. Ben Wheeler of the University of Otago in New Zealand has just published the first in-depth look at what motivates parents who decline the Vitamin K shot for their newborns. The analysis of interviews with 15 families, published in the Journal of Medical Ethics, found a range of factors, from religious beliefs to the conviction that “natural” is better.

“We believe God created us and knew what he was doing,” is one reason Wheeler heard from parents. Others included: “If baby really needed more Vitamin K, they’d get it from me,” and “For us, the risks from Vitamin K were higher because he was such a normal, easy birth.”

“That highlights the false perception among some that if things are natural and easy, that’s a protective factor in some way,” Wheeler said.

Previous research has found a strong link between refusal of Vitamin K and refusal of childhood vaccinations. Research has also found that parents of babies born with the aid of a midwife are likelier to decline Vitamin K.

Some parents don’t want their babies to suffer the pain of the shot, said Dr. Kristi Watterberg, chair of the Committee on Fetus and Newborn of the American Academy of Pediatrics. Some worry about what is in the shot, she said, and some have heard about an old study linking Vitamin K shots to leukemia that has since been refuted.

If you Google “Vitamin K newborn,” one of the first links is to a site that warns of the “potential dark side” of the shot and favors oral treatments instead, even though the American Academy of Pediatrics and the CDC recommend the shot over the oral option.

“There are so many things on the internet that are absolutely not true,” Watterberg said. “They have no basis in fact.”

Parental Ethics

If you’re wondering, “Why not make Vitamin K shots mandatory?” the answer is, New York state does. But the rest of the country allows parents more leeway. Parents are widely granted extensive rights to choose their children’s care, and Vitamin K shots seem to fall into an ethical gray zone.

The central ethical question, Wheeler said, is: “Is there a significant or imminent risk to the individual by the decision they’re making? In particular, when it refers to a child who can’t speak for themselves, then it’s really the doctor’s duty to understand those risks.”

A classic example: If a child is bleeding heavily and parents resist treatment for religious reasons, the doctor clearly must override the parents. But with Vitamin K, Wheeler said, a baby’s risk of hemorrhage without the Vitamin K shot is something like 1 in 1,500, while with the shot it’s more like 1 in 100,000.

And if doctors get overly coercive or forceful about this gray-zone risk, he said, they may damage the doctor-family relationship, with worse consequences down the line.

What Is To Be Done?

Wheeler recommends “a constructive discussion with the family,” at an early point in the pregnancy, ensuring that the information they have is correct and acknowledging that parents “have an ethical right in this zone.”

Dr. Sidonio, of Emory, seconds the call for better communication and is also calling for a national system to track bleeds that stem from Vitamin K deficiency. A preliminary registry is already underway, he said, but it’s likely missing many cases.

He saw his first case of a Vitamin K-deficiency brain bleed seven years ago in an Amish patient in Pennsylvania, but he assumed it was an outlier phenomenon limited to the Amish, he said. Years later, when he was practicing in Nashville and heard about a young baby with a brain bleed, the Amish experience prompted him to check on the patient’s Vitamin K.

He and his colleagues began gathering what turned into that 2013 cluster of cases, and his frustrations grew. Two babies almost died, he said, and “some of the kids had very poor outcomes and were likely to be affected neurologically.” Since 2014, he has seen two cases at Emory as well.

The Vitamin K shot seems to be a victim of its own success, Sidonio said: “When you’ve eliminated a disease or a disorder, many new physicians, new midwives, new doulas, can honestly say ‘I’ve never seen a case.’ ”

Now that Culic, the neonatologist, has seen a case herself, she also sees new urgency behind efforts to persuade patients.

“We should always try to ask parents why they are trying to refuse” the Vitamin K shot, she said, “try to alleviate their fears and explain where the misunderstanding is, and try our best not to let it happen.”