After dreaming for so long about what your baby would look like, now they're here and you're looking into their beautiful eyes, you may be starting to ask another question, 'when do babies' eyes change colour?' All your friends have their own ideas, and everyone thinks they know the science behind it - but we've got all the information you need right here.
When do babies' eyes change colour?
Your newborn's eye colour is unlikely to stay the same. Even if they're born with blue eyes and they stay blue, they'll change subtly as they age. As our expert, retired midwife, baby expert, parenting consultant and author, Rachel Fitz-D notes, "everyone with blue eyes knows that there are shades of blues and often children's blue eyes are 'bluer' when they're born and then go greyer or get a hint of green as they get older."
The most dramatic eye colour changes occur when your child is between the ages of three and six months old. By that point, the iris has enough pigment for you to be able to better predict what the final eye colour will be. But even at 6 months, they may continue to change slightly. Nevertheless, by your baby's first birthday you can be pretty confident that their eye colour is here to stay.
What is eye colour?
Eye colour refers to the appearance of our iris, the muscular ring that surrounds our pupils. It's the iris that helps control the amount of light that enters our eyes. This iris comes in a variety of colours from green to blue, hazel to dark brown.
Like us adults, babies' pupils will always be black, just like how the sclera (better known as the whites) will always be white. This can change however if your child is suffering from jaundice, where they may have yellow-tinged eyes. Equally, if their eyes start to look red, it may be conjunctivitis.
Why do babies' eyes change colour?
As Rachel Fitz-D explains, babies eyes change colour in the early months because newborns aren't born with the levels of melanin they'll eventually have. "The amount of melanin increases over time as the baby is exposed to daylight, and even through childhood and adulthood, eyes change colour subtly." This is why their eyes may be blue when your baby is born but change to another colour in a few months.
What factors determine eye colour?
The physics behind what determines eye colour is fascinating. It's all to do with something called the 'Tyndall effect', which is about the scattering of light and how it can make eyes appear different colours. It's similar to what is called 'Rayleigh scattering' which is what makes the sky look blue.
Melanin
The colour of your baby's irises is to do with something called melanin, a protein secreted by cells called melanocytes which also determines the colour of your skin.
So the colour of your eyes is determined by the amount of melanin in your eyes, which means they are able to absorb more or less light. Simply put, the more melanin you have in your eyes, the darker your eyes will be.
Those with more melanin won't be able to absorb as much light, making their eyes appear dark brown, whereas those with blue eyes will have a tiny amount of melanin, meaning that all the light that enters them is scattered back into the atmosphere, creating a blue hue. Green or hazel eyes are somewhere in the middle.
"Your baby's eyes don't reach their full colour for a while because they haven't had enough daylight so the melanocytes (colour-making cells) haven't been triggered" says Rachel. These melanocytes in the iris secrete melanin in response to daylight so as the baby is exposed to more and more daylight, their eyes will change colour.
Genetics
If you're wondering what colour your baby's eyes will be, you can look in the mirror and at your partner and wider family. That's because the eventual colour of your baby's eyes is largely determined by genetics. There is one specific chromosome that is most responsible for determining your baby's eye colour. This chromosome carries two genes, one of which will determine the amount of melanin in your youngster's iris and the other that controls the activity of the melanocytes, the cell which contains the melanin. Together, these genes work together to determine baby's eye colour.
As a result, this means that you can't necessarily work out your baby's eye colour just by looking at you and your partner's eye colour although you can get a pretty good idea. For example, if you both have blue eyes, it's highly likely your little one will have blue eyes too. But if one of you has brown eyes and the other has blue, your baby might end up with either colour, though the odds are slightly tilted in favour of brown.
"This is all to do with dominant and recessive genes" says Rachel. "The blue gene is recessive while the brown is dominant". As this eye colour activity from Imperial shows, this means that "if you have allele (gene) for brown eyes, you are likely to have brown eyes no matter what other allele you inherit from your other parent." For instance:
• If both parents have blue eyes, it's likely (though not always the case) that you'll have a blue-eyed child
• If you both have brown eyes, you're more likely to have a brown-eyed child
• If one parent has brown eyes and the other has blue eyes, the chances are fairly even that your baby could end up with blue or brown eyes
• If one of the grandparents has blue eyes, the baby has a slightly higher chance of having blue eyes
However, as with most science, it's not really this simple. Your baby's eye colour is made up of around 16 genes, all of which can affect the eventual colour of their eyes. So while you can take a guess at your baby's eye colour based on the colour of yours and your partner's, it's not a foolproof baby eye colour predictor.
And of course, as Rachel notes, "even within the one colour there will be a spectrum of colours. This is all to do with the activation of melanin in the eyes that creates those variations." So the eventual colour of your baby's eyes is unlikely to be exactly the same as its parents.
Are all babies born with blue eyes?
While this is a common belief, not all babies are born with blue eyes. While many Caucasian newborns' eyes appear blue or grey, this is just because they tend to be born with less pigment than other ethnicities. As they are exposed to the light, the eye colour can start to change. Typically, African, Hispanic, and Asian babies are born with brown eyes.
When do babies' eyes stop changing colour?
While your baby will be able to see clearly at around three months old, their eyes will most likely carry on changing colour until around six to nine months. However, they can continue changing colour up to about three years old before it is permanent, and as Rachel Fitz-D tells us, your eyes may continue to change colour very slightly throughout your life.
How can you tell if your baby's eyes will stay blue?
Supposedly, there is a way to tell whether or not eye colour will change by looking at a baby's eye from the side so that there's no light affecting your view. If there are hints of gold in the iris, it means their eyes will probably become brown or green over time. Whereas if the eyes are still very blue, they are likely to stay that way. But the only real way of knowing the colour of your baby's eyes is to wait patiently until they're around a year old.
So keep staring into those big eyes of your little baby - and don't note down the colour in their baby book just yet!
About the expert
Rachel Fitz-D is an active birth teacher, parenting consultant and author of Baby Skin To Skin, with over 30 years working as a midwife and as a parenting consultant. Based in Berkshire, near London, she has appeared on numerous radio programmes, talking about various issues from infant feeding to smacking to humanist parenting. She co-created Henley Birthcare, a unique freelance midwifery and doula service offering bespoke care.
A journalist since 2015, Emily Gilbert is the Features & Reviews Editor for Mother&Baby and has written for the website and previously the magazine for seven years. Emily writes about everything from the top baby products to pregnancy, fertility and maternal mental health. Specialising in product reviews, Emily is the first to know about all the exciting new releases in the parenting industry.