By: Ivan L. Hand, MD, MS, FAAP
There's a lot going on when your baby is first born. They're weighed and measured. Their noses are suctioned out and their vital signs are tested. They may have ointment or drops put in their eyes. They get a complete checkup by your pediatrician.
Most newborns get their first hepatitis B vaccine in the hospital. They also routinely get a vitamin K shot.
But what exactly is vitamin K, and do newborns really need it? Read on to learn more.
What does vitamin K do?
Vitamin K is a fat-soluble nutrient that helps our bodies make blood clots. We need blot clots to stop bleeding. Vitamin K is important for keeping bones healthy too.
Adults and older children get vitamin K from food such as green, leafy vegetables, meat, dairy and eggs. The healthy bacteria in our intestines, which make up our microbiome, also produce some vitamin K.
Babies, though, have very little vitamin K in their bodies at birth. This puts them at risk for bleeding. Fortunately, it's easy to prevent VKDB with a vitamin K shot. The injection is given in your baby's thigh within 6 hours of birth.
One shot is all it takes to protect your baby from getting vitamin K deficiency bleeding. This is why, as pediatricians, we have recommended since 1961 that all newborns get a vitamin K shot at birth.
Why babies aren't born with enough vitamin K?
The two big reasons newborns need vitamin K:
They don't get much vitamin K from the mother during pregnancy. Unlike many other nutrients, vitamin K doesn't pass through the placenta very easily.
Babies' intestines don't have very many bacteria yet, so their bodies can't make enough vitamin K.
What is vitamin K deficiency bleeding?
Newborns who don't get a Vitamin K shot and are low on the vitamin are are at risk of vitamin K deficiency bleeding (VKDB). This happens when a baby's blood can't make clots, and their body can't stop bleeding.
The bleeding can happen on the outside of the body. It can also happen inside the body where parents can't see it. A baby could be bleeding into their intestines or brain before their parents know anything is wrong. Brain bleeding happens in about half of all babies who develop VKDB, and it can lead to brain damage or death.
There are three types of vitamin K deficiency bleeding:
Early-onset: This begins within the first 24 hours after birth. It usually happens when the mother is taking certain medications that interfere with vitamin K.
Classical: This happens between 2 days and 1 week after birth. Doctors don't know exactly what causes most of these cases. Early-onset and classical VKDB occur in 1 in 60 to 1 in 250 newborns.
Late-onset: This happens between 1 week and 6 months after birth. It's rarer than early-onset or classical VKDB, occurring in 1 in 14,000 to 1 in 25,000 babies. Infants who didn't get a vitamin K shot at birth are 81 times more likely to develop late-onset VKDB than babies who do get the shot.
Cases of VKDB seem to be increasing. This is partly because more parents are refusing the vitamin K shot for their newborns. VKDB is fairly rare, so many parents aren't aware of how dangerous the effects of this disease can be.
Are vitamin K shots safe?
Yes, vitamin K shots are very safe. The vitamin K from the injection is stored in your baby's liver and released slowly over months. This gives your baby the vitamin K they need until they can start getting it from solid food and making it themselves.
You may have heard about a study from the 1990s about a possible link between the vitamin K shot and developing childhood cancer. This didn't only worry parents; doctors and scientists were concerned too. Since then, experts have done many different kinds of studies to verify this link. None of the studies have ever been able to find that link again.
Can my newborn get oral vitamin K instead?
Some parents may ask for oral vitamin K instead of the shot. But babies can't absorb the oral form very well, so it doesn't work well to prevent VKDB. A vitamin K shot is the safest and best option for all newborns.
Does breastfeeding give my baby vitamin K?
Breast milk does give your baby a little bit of vitamin K. But it's not enough to prevent VKDB. Babies who are exclusively breastfed are at higher risk of developing VKDB because their vitamin K levels are low.
This all changes when your baby is old enough to start eating solid foods, usually between 4 and 6 months. The bacteria in your baby's intestines will also start making vitamin K once they're eating solid foods.
What are the signs of vitamin K deficiency bleeding?
In most cases, there aren't any warning signs to let you know beforehand that something serious—and possibly life-threatening—is happening.
When babies develop VKDB, they might have one or more of these signs:
Bleeding from the umbilical cord or nose
Paler skin or, in dark-skinned babies, pale gums
Bruising easily, especially around the face and head
Bloody stool or black, dark, sticky stool
A yellow tint to the white parts of the eyes 3 weeks or more after birth
Seizures, irritability, excessive vomiting or sleeping too much
It's easy and safe to prevent VKDB with a vitamin K shot at birth. If you have any questions or concerns, be sure to talk to your pediatrician. They can help you weigh the benefits and risks.
About Dr. Hand
Ivan L. Hand, MD, MS, FAAP, is Director of Neonatology, Kings County/Health & Hospitals and a Professor of Pediatrics at SUNY-Downstate School of Medicine. He was selected as a 2022 New York Super Doctor and is a member of the Society for Pediatric Research. Within the American Academy of Pediatrics (AAP), Dr. Hand is a member of the Committee on Fetus and Newborn.