Why Do Newborns Need a Vitamin K Shot?

I'm pregnant with my first child, and my OB told me that my baby will get a shot of vitamin K right away. Is this really necessary?
– Nina

Yes, health experts recommend that all newborns get a dose of vitamin K at birth. Babies aren't born with enough of this important vitamin, which is needed for blood to clot normally.

Babies who don't get vitamin K at birth are at risk for a potentially fatal bleeding disorder called vitamin K deficient bleeding (VKDB). VKDB can cause bruising or bleeding in nearly every organ of the body. Almost half of VKDB cases involve bleeding in the brain and brain damage.

Babies are at risk for VKDB for the first 6 months of life. That's because most of the vitamin K the body makes comes from the foods we eat and the healthy bacteria in our intestines. Until they start eating solid food at about 6 months of age, babies don't have enough naturally produced vitamin K. And nursing moms don't pass enough vitamin K in their breast milk to protect their babies from VKDB.

You may have seen or heard comments from parents who don't want to get the shot for their baby. This is because there's still old information going around from a small study in the early 1990s. That study suggested a link between the vitamin K shot and cancer. Larger studies since then have found no connection between vitamin K and cancer. But the outdated information can still be found online. 

Some European countries let families choose an oral form of vitamin K. But this is far less effective than the shot at preventing bleeding, especially in the brain. Oral vitamin K is not available for newborns in the United States.

No parent enjoys the thought of their little one getting a shot. But a single injection of vitamin K can protect a baby from a serious, even deadly preventable bleeding disorder. The Centers for Disease Control and Prevention (CDC) has more info about the vitamin K injection and VKDB.