Babies are born with a deficiency in vitamin K, an important factor for proper blood clotting. So most newborns are given a shot of vitamin K soon after birth to prevent potentially life-threatening hemorrhages in the brain or intestines.
It's been standard practice since the early 1960s, but the rise in anti-vaccination rhetoric has also created a distrust around the vitamin K shot. And it's all too easy to find risky or just plain false information. Search "vitamin K shot" on Google and some of the top results caution against them.
It's a similar story on Facebook. The same search reveals a mix of posts, some providing inaccurate information about the vitamin K shot.
In one study, researchers surveyed parents who intended to refuse the shot and found that most were white, college-educated people over 30. In addition to the vitamin K shot, 90% refused the hepatitis B vaccine. Their concerns included "toxic" ingredients, excessive doses, and side effects. Most of them — 70% — got their information from the internet.
But there are potential health risks for babies whose parents skip the shot, according to Dr. Mark Hudak, the chair of the pediatrics department at University of Florida College of Medicine–Jacksonville.
He told BuzzFeed News that the vitamin K shot protects against bleeding in the first 24 hours (early onset), at 2 to 7 days (classic onset), and 2 weeks to 6 months (late onset). Early excessive bleeding, which happens in about 1% of babies, can occur in a number of ways, including in the intestines or mucus membranes, or after something like a circumcision.
Later bleeding can involve serious hemorrhaging in the brain that can be life-threatening or cause lifelong disability.
"Even if it is treated, it can produce lifetime neurological problems," Hudak said.
This later bleeding is more rare, affecting about 5 in every 100,000 babies, but Hudak pointed out that that's still 200 of the 4 million babies born every year in the US. So to him, skipping the vitamin K shot makes no sense.
"In the vast scheme of things is that worth 200 babies a year having severe brain bleeds and neurological deficiencies?" he said.
"Is that acceptable? I would say it's not, it's going to backwards."
According to the Centers for Disease Control and Prevention, the risk of developing VKDB is estimated to be 81 times greater for babies who do not receive the shot, compared to the ones who do. About 1 in 5 infants with VKDB will die of it. The condition is now rare, but that's only because of the vitamin K shot.
Some of the anti–vitamin K misinformation found online claims that women can simply eat a vitamin K–rich diet before delivery and when breastfeeding. But Hudak said that won't cut it because breast milk carries very little of the nutrient, and it doesn't easily cross the placenta, according to the CDC.
"The mother can eat all the broccoli she wants but she's not going to pass very much vitamin K in her breast milk," he said.
There's also the issue of orally administered vitamin K, which some parenting blogs claim is better, or more "natural." Again, Hudak said that won't do it. Studies have shown variable absorption among babies given oral vitamin K, and a delay in digestion.
The vitamin K shot, on the other hand, is delivered intramuscularly, and works over a period of 4 to 6 months.
He also said that there was concern in the 1990s of a link between the shot and later development of leukemia, but studies debunked that association long ago.
Still, despite the science behind it, Hudak recognizes that it can be hard to convince parents who've gone down an anti-medicine rabbit hole.
"Even if you can convince them on the facts, and they're willing to accept that the science shows that there's not a downside of giving the vitamin K, you still have to deal with this philosophical, overarching mantra that a lot of these parents come in with," he said.