Vitamin K for Newborns: How it was discovered & why it matters

By Dr. Sarah Slater, DNP, APRN, CPNP-PC, ECS Specialist

Understanding Vitamin K and Newborn Health

Vitamin K plays a critical role in blood clotting, yet many parents first encounter it only after their baby is born. To understand why vitamin K is recommended for newborns today, it helps to look at how it was discovered and how its absence led to serious bleeding in infants long before modern prevention existed.

Vitamin K Deficiency Bleeding Before Routine Prevention

Before vitamin K was routinely given to newborns, serious bleeding events were far more common. Medical literature from the late 1800s and early 1900s describes infants who appeared healthy at birth but developed sudden, severe bleeding days or weeks later. These unexplained events eventually became known as Hemorrhagic Disease of the Newborn (HDN).

Historical estimates suggest that between 0.25% and 1.7% of newborns experienced HDN, with no clear explanation at the time. While this percentage may appear small, the most concerning aspect was the unpredictability, there was no reliable way to identify which infants would be affected.

When bleeding occurred, outcomes could be devastating. Some infants died, particularly when bleeding involved the brain. Others survived but were left with permanent complications such as seizures, developmental delays, or motor impairment.

The Discovery of Vitamin K and Its Role in Blood Clotting

Vitamin K was not identified until the early 1930s, when Danish scientist Henrik Dam was studying the role of fat in nutrition. To better understand how fat functioned in the body, he conducted experiments on chickens in which he removed fat from their diets.

Eliminating “fat” did not simply mean removing oils or butter. It removed an entire group of fat-dependent substances, including triglycerides, fatty acids, cholesterol, fat-soluble vitamins (A, D, E, and K—though these had not yet been identified), and other lipid compounds.

As Dam’s experiments progressed, he observed something unexpected: the chickens began developing severe, unexplained bleeding.

Researchers initially suspected cholesterol deficiency and reintroduced cholesterol into the diet. . . The bleeding continued.

The cause became clear only when an unidentified fat-soluble substance was added back, at which point the bleeding stopped entirely. This substance was later identified as vitamin K, named from the German word Koagulation, meaning coagulation or blood clotting.

For this discovery, Henrik Dam was awarded the 1943 Nobel Prize in Physiology or Medicine, shared with Edward Adelbert Doisy, who helped identify vitamin K’s chemical structure.

Linking Vitamin K Deficiency to Newborn Bleeding

As researchers gained a clearer understanding of vitamin K’s role in coagulation, clinicians began noticing striking similarities between vitamin K deficiency and Hemorrhagic Disease of the Newborn. This led to the hypothesis that newborns might be especially vulnerable to vitamin K deficiency bleeding.

Over time, clinicians demonstrated that insufficient vitamin K in newborns could directly result in bleeding from the umbilical stump, gastrointestinal tract, and skin, and, most concerning, bleeding inside the brain.

Further research confirmed that vitamin K deficiency, rather than birth trauma or inherited clotting disorders, was the true underlying cause of Hemorrhagic Disease of the Newborn.

Once this connection was established, studies showed that administering vitamin K shortly after birth dramatically reduced the risk of severe and life-threatening bleeding, fundamentally changing newborn care and prevention strategies.

Why Newborns Are Naturally Low in Vitamin K

Newborns are born with very low, often nearly undetectable, levels of vitamin K. This vulnerability exists for several reason:

• Minimal vitamin K crosses the placenta during pregnancy.

• Newborns lack the gut bacteria needed to produce vitamin K.

• Breast milk contains low levels of vitamin K, even when mothers supplement.

• Infants cannot yet consume vitamin K-rich foods.

Because of this, it takes weeks for an infant to naturally accumulate enough vitamin K to support normal blood clotting. During this period, infants remain at risk for Vitamin K Deficiency Bleeding.

The Three Types of Vitamin K Deficiency Bleeding (VKDB)

1. Early VKDB (First 24 Hours of Life)

Most often seen in infants whose mothers have low vitamin K levels. This may result from medications that interfere with vitamin K metabolism or maternal conditions that impair absorption.

2. Classic VKDB (Days 2–7 of Life)

Classic VKDB typically occurs between days 2 and 7 of life and is often associated with low vitamin K intake.

3. Late VKDB (2 Weeks to 6 Months)

Although rare, late VKDB is the most dangerous form as bleeding frequently occurs in the brain, resulting in severe or permanent injury. It may be associated with conditions that affect vitamin K absorption, but it can also occur in otherwise healthy infants.

Why Vitamin K Still Matters Today

When routine vitamin K prophylaxis was introduced in the mid-1900s, rates of Vitamin K Deficiency Bleeding dropped by more than 90%, and deaths from this condition became rare in countries using standard prevention.

However, when vitamin K is declined, VKDB still occurs. Modern case reports closely resemble the severe bleeding patterns documented before supplementation existed.

The risk has not changed — our ability to prevent it has.

Coming Up in Part 2

In Part 2, we’ll examine how misinformation about vitamin K developed, why it continues to circulate, and how parents can evaluate claims using evidence rather than fear.