Once your baby’s eyes are exposed to more light, they may start to deepen in hue or change color altogether, usually between 3 and 9 months

You can’t wait for that first look at your sweet newborn baby, when you’ll take in everything about them. Just don’t get too accustomed to their eye color … because it might change!

Ophthalmologist Nicole Bajic, MD, explains why and when babies’ eyes change color.

The science behind changing eye color

Eye color refers to the color of your irises, a ring of muscle tissue around your pupil (that black spot in the center of your eye) that controls how much light enters your eyes. In the uterus, of course, fetuses don’t get much light exposure. After all, it’s pretty dark in there!

“When they’re born, a baby’s eyes — specifically cells in the iris called melanocytes — are exposed to light,” Dr. Bajic explains, “and that produces pigment, or color.”

As your baby gets older and is exposed to more light, the color of their eyes can start to change, from deepening in hue to changing color altogether.

“Darker colors like brown typically have more melanin, the pigment that determines pigmentation in our skin and eyes and hair,” Dr. Bajic says. “Darker eye colors, like brown, have more melanin, and lighter colors, like blue, have less.”

Are all babies born with blue eyes?

It’s a myth that all babies are born with blue eyes. In fact, one study found that just over 20% of babies studied were born with blue eyes, while a whopping 63% of them were born with brown eyes.

Plus, being born with blue eyes doesn’t guarantee growing up with blue eyes.

“Many babies have lighter, blue-gray eyes due to less pigment in their irises,” Dr. Bajic notes, “but as they get older, many will change color.”

Desperate to know what color your child’s eyes will be? While you may not be able to determine it from birth, genetics can clue you into what’s likely.

“The basis for eye color is determined genetically, meaning you get it from your biological parents,” Dr. Bajic explains. “If both parents have blue eyes, there’s a 99% chance the baby will, too. It’s less likely that two brown-eyed parents will have a blue-eyed baby, but it’s possible, especially if they have grandparents with blue eyes.”

There are, of course, other eye color possibilities, too, including green, gray, amber and a brown/green mix known as hazel. Some people even have two different-colored eyes, a condition called heterochromia (which may be present at or soon after birth).

When to expect your baby’s final eye color

“Eye color starts to change as kids get older, between 3 to 9 months — often around 6 months,” Dr. Bajic shares. “But it can take up to three years until their final eye color is determined.”

Beyond that, any sudden change in eye color in children or adults can be a sign of a medical concern that should be raised ASAP with an ophthalmologist.

Only time will tell what color your child’s eyes will be, so you’ll have to be patient. But time flies when you’re raising a little one, and they’ll be a toddler before you know it — so just enjoy the wait!