Genetics can explain how eye colour is inherited and the odds of your baby having certain eye colours. But at the end of the day, it is just a guessing game and you will have to wait for your bundle of joy to arrive to get your answer. If you are surprised by this piece of information, there’s more to come! Your baby’s eye colour can even change in the first six months after birth!
What determines eye colour?
The presence of a pigment known as melanin, in the iris of the eye, determines eye colour (melanin also determines the skin colour in humans). Babies with low melanin content have light eyes and those with high melanin content have darker eyes. In the eye colour spectrum, you have blue eyed babies at one end of the spectrum while brown or black eyed babies occupy the other end. Between the two extremes, there are other eye colours like green, grey and hazel. Sounds interesting and mind boggling at the same time, doesn’t it?
A lack of melanin causes albinism characterized by red eyes and very pale hair and skin. In rare cases, a condition called heterochromia results, where the baby has two different coloured eyes. Don’t get a horrifying mental image – consider beautiful ‘Black Swan’ actress Mila Kunis and star of ’24’ Kiefer Sutherland, two notable celebrities with heterochromia.
How much melanin the iris will have is decided by gene combinations from the mum and dad. Such combinations are impossible to predict. So, even if you and your spouse have green eyes, there is a chance that your baby may have brown eyes (a less than 1% possibility, but a possibility nevertheless). The best advice we can give is – be prepared for surprises!
The genetics of eye colour
Each parent contributes one copy of the colour genes to the baby. Each gene has an allele, the dominant ‘B’ allele for darker eye colour brown and the recessive ‘b’ for lighter colour blue. The two alleles combine to determine the eye colour in the baby. The baby can inherit any allele from each parent, which ultimately decides the eye colour. In short, you have better luck predicting the weather than your baby’s eye colour!
Suppose the father has brown eyes (Bb or BB) and the mother has blue eyes (bb). Then the baby will have blue eyes if both parents pass on the ‘b’ gene or brown eyes if the father passes on the ‘B’ gene. In a different case, both brown-eyed parents with Bb genes can pass on the recessive -b’ each to give their baby green or blue eyes. The next time you see the offspring of an Asian or African American couple having green eyes, you will know that the recessive gene had a big role to play.
These are simple examples. For hazel and the extremely rare amethyst coloured eyes, the gene combinations and resulting colour can be best explained by expert geneticists. But it has been observed that the possibilities of brown-eyed and black haired parents producing dark haired and dark eyed children are higher (ditto for light eyed parents).
Change in eye colour
A baby born with light blue eyes may not retain the same colour when he or she grows up. The baby’s eyes don’t produce pigment when it is in the womb. So, most babies will have light blue eyes at birth. Don’t go waxing eloquent about how your baby inherited his daddy’s gorgeous blue eyes, someone may politely point out that the lack of melanin has more to do with it than daddy dearest!
In the six to twelve months following birth, the baby’s eye colour will darken. The darkening is due to the fact that the exposure to sunlight stimulates pigment production, which is responsible for the darker colour (if you have been an attentive parent, you’ll notice the colour change!). This is only in the case of light eyed infants. There will be no colour change in black or brown eyed babies.
Changes in eye colour into adulthood have also been reported, but this stands at a low 10%. As every child has its unique genetic make-up and biology, there really is no sure fire way of predicting how and when eye colour can change. If you are really keen to see if there has been a colour change in your baby’s eyes and to what extent, try to take photographs to notice the difference.
Eye colour doesn’t matter, eye health does
Whether the baby will take after the mother or father is a topic of discussion for most families (be ready with a list of positive characteristics your baby can inherit from you!). But you should keep in mind that the eye health of your baby is more importance than eye colour and other physical attributes. Get your baby’s eyes checked periodically by a qualified ophthalmologist and seek timely help if you spot any abnormalities.