Among the thousands of questions we ask ourselves when we’re pregnant, the baby’s eye color is one of the most common. Especially when one of the parents or grandparents has light eyes. The desire for the baby to inherit the beauty of blue eyes is inevitable. But do you know what determines your baby’s eye color and which factors are important for this determination1?
In the first days of life, babies’ eyes are usually grayish, almost blue, which increases the family’s anticipation even more. As the days go by this color changes and settles into blue, green, or brown, gradually getting closer to the true color they will have. So, don’t be fooled if you see completely light eyes at birth, everything can change over the following months. The determining factor for the baby’s eye color is the melanin in the iris of the eyes2, and when babies are newborns, the amount is still very low. As it becomes regulated, the color begins to take shape. The iris is located just behind the cornea, with the pupil at its center. The pupil is always black because it is actually a small opening through which light enters. Some genetic problems can also alter iris color, such as albinism, which, due to low melanin, can result in pink eyes, for example, or very light blue eyes.
Usually, a baby’s eye color starts to change and approach its permanent shade around 3 to 6 months of age. After that, it is fully defined by the time they reach their first year. Eye color is entirely genetic and determined by hereditary factors, but unfortunately it isn’t possible to state with certainty what color eyes your child will have. After all, there are various probabilities with margins for error or changes. The gene that determines the baby’s eye color is set as soon as fertilization occurs! The DNA defines it as soon as the two (sperm and egg) cells meet3. The greatest influence is the dominant gene from either parent. Brown eyes are dominant genes, while lighter colors are the so-called recessive genes. But genetics can still bring many surprises!
Father+Mother | Probability |
Brown + Brown | 75% brown/19% green/6% blue |
Green + Brown | 50% brown/37% green/12% blue |
Blue + Brown | 50% brown/0% green/50% blue |
Green + Green | -1% brown/75% green/25% blue |
Green + Blue | 0% brown/50% green/50% blue |
Blue + Blue | 0% brown/1% green/99% blue |
How to Calculate Baby’s Eye Color
As we’ve mentioned, the baby’s eye color is determined by hereditary factors where the genes of parents and relatives play a big role. That’s why it’s possible to have a prediction of what color eyes your baby will be born with, but again we stress that it isn’t 100% guaranteed.
- Father and mother with brown eyes are very likely to have a baby with brown eyes;
- Father and mother with blue eyes are very likely to have a baby with blue eyes;
- Father and mother with brown eyes, but with one grandparent who has blue eyes, there is a chance the baby will have blue eyes;
- If one parent has blue eyes and the other has brown eyes, the darker color is more predominant.
The mixing of races and ethnicities means that increasingly babies are born with different eye colors, just as with the shade of their skin and hair. Some countries or cities have a greater number of people with lighter skin, blond hair, and lighter colored eyes, such as Germans and, in the case of Brazil, people living in the South of the country.