Why Your Newborn Needs a Vitamin K Shot

Given shortly after birth, Vitamin K shots can protect your newborn from life-threatening complications. Read about the benefits, side effects, and more.

An image of a nurse examining a newborn in a hospital.
Photo: Getty Images.

After your newborn has emerged into the world, you'll need to decide whether to administer a Vitamin K shot. It may be difficult to think straight after giving birth, much less make big decisions about your baby's health, so it's smart to read up on this important shot before you head to the hospital.

Here's something to think about: "Two out of every 100 babies who do not get a vitamin K injection at birth might have vitamin K deficiency bleeding (otherwise known as VKDB), and one in five babies with VKDB will die," says Rebekah Diamond, M.D., a pediatric hospitalist in New York City and Assistant Professor of Pediatrics at Columbia University, author of the forthcoming book Parent Like a Pediatrician.

What's more, the Centers for Disease Control and Prevention (CDC) says that "newborns who do not get a vitamin K shot are 81 times more likely to develop severe bleeding than those who get the shot."

Browse this article to learn about the Vitamin K shot for babies, including when they'll get it, why they need it, and what can happen if you opt out of it.

What is Vitamin K?

Vitamin K is produced by bacteria in the intestine, and it's essential for clotting and stopping serious bleeds. "Newborns—even full term, healthy newborns—have livers that don't make enough vitamin K," says Dr. Diamond. Adults can get the vitamin K they need by eating a healthy diet that includes leafy green vegetables. But newborns have low reserves of vitamin K at birth, according to Dr. Diamond, which is why they need a shot of vitamin K shortly after birth.

Why Does My Baby Need a Vitamin K Shot?

Vitamin K takes time to develop in newborns, who have naturally low levels of it. "What's more, newborns can't benefit from healthy levels of vitamin K in the birthing parent, since it doesn't tend to transfer well through either the placenta or through breast milk," says Dr. Diamond.

When babies experience low levels of vitamin K, they're at risk for a life-threatening condition called vitamin K deficiency bleeding (VKDB). "This can lead to unpredictable fatal bleeding that can occur without warning or specific incident during the first few months of life, most commonly in the baby's brain or intestines," Dr. Diamond says.

According to the American Academy of Pediatrics (AAP), which has recommended vitamin K shots since 1961, most cases of VKDB occur between two days and one week of life. Early-onset VKDB begins within 24 hours after birth, while late-onset VKDB happens between one week and six months of age.

The CDC says babies up to 6 months of age can suffer from VKDB. "The risk isn't limited to just the first 7 or 8 days of life and VKDB doesn't just happen to babies who have difficult births," says the organization.

When Is The Vitamin K Shot Given?

Because of the scary consequences of low levels of vitamin K in newborns, the shot to deliver Intramuscular (IM) vitamin K is generally administered shortly after birth, says Jaspreet Loyal, M.D., MS, Associate Professor of Pediatrics and Division Chief of Pediatric Hospital Medicine at Yale Hospital. "The timing might vary depending on the hospital, but in general, it is given in the first few hours of life."

Does the Vitamin K Shot Have Side Effects?

The vitamin K injection in newborns is very safe, says Dr. Loyal. "In my 10 years as a pediatric hospitalist, I have never seen an adverse reaction to the injection."

Side effects are the same as any other shot, says the CDC, and they include pain, bruising, or swelling at the injection site. Allergic reactions are extremely rare (only one case has ever been reported).

Most childhood vaccines are subject to myths and conspiracies, and the vitamin K shot for babies is no exception. In 1990, a small study reported a possible association between the vitamin K shot and the occurrence of childhood leukemia. Rest assured that this study has been debunked several times, says Dr. Loyal, who asserts, "There is no association between the vitamin K injection and leukemia."

A study published in The New England Journal of Medicine came to the same conclusion. "We found no association between exposure to vitamin K and an increased risk of any childhood cancer or of all childhood cancers combined, although a slightly increased risk could not be ruled out," said the researchers. "Unless other evidence supporting an association between vitamin K and cancer appears, there is no reason to abandon the routine administration of vitamin K to newborns."

What Might Happen If I Skip the Vitamin K Shot?

Today, many parents strive to fully understand the potential consequences of any vaccine given to their baby, so it's understandable to have some hesitancy about shots. But refusing the vitamin K shot for your baby is a decision that should be weighed very heavily, says Dr. Diamond. "VKDB can happen any time and is impossible to predict. It can happen suddenly and is impossible to cure, even if vitamin K is given when it happens. It can lead to permanent brain damage and death."

Dr. Loyal agrees, saying, "Parents considering opting out of the vitamin K injection should have a discussion with their pediatrician, ideally prior to delivery, to make an informed decision."

Here are some factors to consider when deciding whether or not to give your infant the vitamin K shot:

  • Some U.S. states have legislation mandating the administration of the vitamin K injection.
  • Most physicians performing a procedure, such as a circumcision, require the newborn to have received the vitamin K injection.
  • Oral Vitamin K supplements do not work as well as the injection in preventing VKDB

The Bottom Line

As your due date approaches, research the vitamin K shot to see if it's right for your little one (but know that most medical experts highly recommend the shot). Never hesitate to reach your OB-GYN or your baby's future pediatrician if you have questions as you strive to ensure your baby is as healthy as possible.

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