Before the phrase “baby blues” came to refer to postpartum sadness (which is not the same as postpartum depression), it was actually a common synonym for “eyes.” Why? Well, because all babies are born with blue eyes, right?

Wrong. Feast your baby blues upon this fun fact: Worldwide, more newborns have brown eyes than blue.

And while it’s true that many babies have blue or gray eyes at first, it’s important to know that eye color can change for months after birth. And there are plenty of infants gazing out at their new surroundings with hazel and brown eyes, too.

In fact, a 2016 Stanford University study involving 192 newborns found that nearly two-thirds of them were born with brown eyes, while only about 1 in 5 babies arrived with blue eyes.

The Stanford researchers also noted, however, that the majority of babies in the study born with blue eyes were Caucasian. Those of other ethnic groups, including Asian and Hispanic, were more often born with brown eyes.

The term “eye color” refers to the color of the iris, the ring around the pupil, which is black. The white part of the eye is called the sclera. If your baby had jaundice at birth — don’t worry, this isn’t uncommon — the sclera may have been a little yellowish.

What gives an iris its color is a natural pigment called melanin, a protein secreted by special cells called melanocytes. Blue eyes mean there is little melanin in the iris.

Melanocytes respond to light, and since your newborn has spent the last several months in total darkness, there wasn’t much light to trigger melanin production in the irises. (Though remember, ethnicity also comes into play — so some babies will produce more melanin than others. More on that in a second.)

If your child’s melanocytes don’t secrete much more melanin in the months and years ahead, then their eyes will stay blue. If a little more melanin makes its way into the iris, their eyes will look green or hazel. A lot more melanin means brown eyes.

But for many babies in the womb — including, specifically, many babies of non-Caucasian descent, though this can be true for any ethnicity — melanocytes don’t need the light of day to pump melanin into those developing irises. These are the brown eyes that greet so many smiling parents.

Layers of color

The iris has three layers, and people with brown eyes have melanin in all three.

A blue-eyed person has brown pigment in the back layer only. As light enters the eye, most of the light is absorbed in the back layer, while particles in the spongy middle layer (stroma) scatter the remaining light reflecting back out of the eye.

Most of that scattered light that gets back out is blue light, giving blue eyes their color. It’s the same dynamic that makes water in an ocean look blue.

Those influential melanocytes are also hard at work in hair and skin, giving them their colors, too. More melanin in your system means a darker complexion. This explains why people with darker skin tend to have darker-colored eyes, too.

But there are always exceptions. Acclaimed African American actor James Earl Jones, for example, has blue eyes, likely the result of having ancestors of European descent with blue eyes.

And speaking of ancestors, let’s take a look at what goes into determining what your baby’s final eye color will be.

Your baby’s first eye color may be permanent. But don’t get too attached to it. Eye color often changes during the first year or even longer. That means your blue-eyed newborn may have brown eyes by the time they take their first steps.

There’s no way to know when the final color will be set. And the exact color can’t be predicted by you any easier than it can be by a Magic 8 Ball. But if you’re looking for clues and if it’s possible, stand with your baby’s other parent and look in the mirror together.

While melanin is what technically gives the eyes their color, it’s the eye colors of a baby’s parents — and to a certain extent, of your great-great-great uncle and your great grandma and all the others in that big family tree of yours — that help determine the amount of melanin that is secreted.

The genetics are somewhat complicated. But in simple terms, two blue-eyed parents, for example, are more likely to have a blue-eyed baby. But there are no guarantees. Likewise, parents with brown eyes will usually produce a brown-eyed child, but not always. The eye color of a grandparent can change the odds a little.

While it was once believed that parents with brown eyes could not produce a child with blue eyes, it can — and does! — happen, thanks to multiple genes at work.

Check out some of these eye color stats:

  • Blue eyes are a relatively new phenomenon. Researchers traced blue eyes to a single genetic mutation that occurred between 6,000 and 10,000 years ago.
  • Though estimates vary, fewer than 200,000 people in the United States have a rare condition known as complete heterochromia or heterochromia iridis, where one eye is a complete different color than the other eye. If you or your baby has this unique trait, you’re in good company — actresses Alice Eve and Mila Kunis have it as well.
  • Also rare is a disease called Waardenburg syndrome, which affects 1 out of 40,000 people. People with this condition often have differently colored eyes, and other symptoms include hearing loss and white patches of hair and skin. So while having this syndrome is pretty unlikely, if your baby is born with very pale blue eyes or one blue eye and one brown eye, talk with your doctor.

From very first eye contact, you were mesmerized by your baby’s eyes — and every other trait, too. If you were startled to see blue eyes staring back at you, we hope we’ve eliminated some of the surprise you might otherwise experience later if those same eyes are brown.

Melanin determines several aspects of our appearance. And while we have the least amount when we enter the world for the first time, remember that babies may be born with eyes of blue, brown, hazel, green, or some other color. It’s simply a myth that all of us — or most of us, for that matter — are blue-eyed at birth.

As with everything else involving your newborn, enjoy each stage as it comes — yes, even the “terrible twos” — and know that eye, skin, and hair color will become things that make your child uniquely beautiful.