What role do genetics play in baby eye colour? Is there a way to predict what colour they’ll be? Is it true they can change? We’ve got the scoop.
New parents can spend a lot of time gazing into their baby’s beautiful eyes—and wondering about their colour. Will it stay the shade they’re born with, or will it change? We spoke to experts to find the answer to all your baby eye colour questions!
Will my baby’s eye colour change?
It might! Most babies with lighter skin are born with blue or grey eyes. Some stay blue or grey while others gradually change over time to green, hazel or brown. Most, but not all, babies with darker skin are born with darker eyes that stay brown.
What determines a baby’s eye colour?
The coloured part of the eye, the iris, contains a protein called melanin—the same protein that affects skin colour. The melanin comes from specialized cells called melanocytes. As your baby ages, the melanocytes respond to light, producing melanin. The more melanocytes at work, the darker the eyes become. It’s worth remembering that there isn’t actually blue or green pigment in the iris. Everyone has melanin in the back layer of the iris. People with brown eyes also have some melanin in the front layer of the iris. This melanin absorbs more light and makes the iris look brown. People with blue, grey or green eyes have little to no melanin in the front layer of the iris. Hazel eyes (a combination of green and brown) have a small amount of melanin in the front layer of the iris.
Baby eye colour progression
Eye colour starts to change in baby’s first six months, says Kirsten North, an optometrist in Ottawa. “I’d say by nine to 12 months, for the majority of babies this colour is locked in. In a minority of kids, though, eye colour can keep getting darker up until age five or six.” As melanin is added to the iris, the colour changes from blue or grey to green or hazel, and then brown, she says. “Where you stop on that continuum is in your genes.” The darkening is gradual and affects the whole iris, not just flecks or spots.
Will my baby’s eyes stay blue?
You can’t tell for sure, but if you and your partner both have blue eyes, your baby is more likely to have blue eyes too. Grandparents who also have blue eyes increase the odds of a blue-eyed baby too. (North adds that there is no truth to the myth that keeping your baby in the dark for the first few months will mean they keep their blue eyes!)
What role do genetics play in eye colour?
What many of us learned in high school biology class about eye colour genetics isn’t considered correct anymore. According to the National Institute of Health, scientists used to believe that eye colour was determined by just one gene, which followed a simple pattern where brown eyes were dominant (or “won”) over blue eyes. However, “There’s more than one gene that affects eye colour,” explains North. “It’s complicated, not just one gene from each parent.” There are about 16 genes involved in eye colour, reported in a 2011 article in the Journal of Human Genetics. Work by Australian researchers suggests that of the multiple genes involved in eye colour, there are two major genes, one that controls for brown or blue, and another that controls for green or hazel, plus there are other genes that modify these tendencies too. What does this all mean? The particular combination of genes that you and your partner have ultimately affect your kid’s eye colour. (So don’t put up with any snarky comments from family members about parentage.)
Is there a way to predict my baby’s eye colour?
Not really. Two brown-eyed parents are likely to have a brown-eyed child, but could potentially have a child with blue, green or hazel eyes, depending on the combination of genes from each parent. Two blue- or green-eyed parents are likely to have a child with blue or green eyes (or a blueish-greenish combo), but it’s possible they will have a brown- or hazel-eyed child. If one parent has darker eyes and the other has lighter eyes, they are slightly more likely to have a child with darker eyes, says North.
What about two different eye colours?
Having two different eye colours is called heterochromia, and it refers to two eyes that are totally different colours (often one blue and one brown) or one eye that is mainly one colour and also has a distinct patch of another colour in it. Different coloured eyes can be present at birth, or can develop over the first year, says North. Why does it happen? “It’s such a rare condition that I don’t think the genetics have been fully mapped out yet,” she says. (Fun fact: Celebrities with heterochromia include Mila Kunis, Kate Bosworth, Kiefer Sutherland, Jane Seymour, Bill Pullman and Henry Cavill.) North cautions that if your child does develop a different coloured eye or portion of an eye, you should get that checked by an optometrist to rule out rare but serious issues like an injury to the eye or a melanoma.
What are the most common eye colours?
About 79 percent of the world has brown eyes, according to Worldatlas.com. Another 8 percent or so have blue eyes (believed to be caused by a genetic mutation about 10,000 years ago). Amber (yellowish-brown) or hazel (greenish-brown) eyes are found in another 5% of the population each. Green-eyed people make up only 2 percent of the population. The final one or two percentage points include grey eyes, and, rarely, red or purplish eyes in people with albinism (where melanin levels are so low that blood vessels show through).
Your baby changes so much in the first year, and for some kiddos their eye colour changes too. Whether eye colour changes or not, keep on enjoying locking eyes with your little one.