If you are wondering what colour your baby's eyes will be, we can offer some clues. Progress in genetics allows eye colour to be predicted before birth using simple inheritance rules.

If both parents have blue eyes
Because the allele for blue eyes is not dominant, blue-eyed parents each have two copies of it. The baby therefore inherits a blue-eye allele from each parent and will have blue eyes. (Case 1)

If one parent has blue eyes and the other has brown eyes
A brown-eyed parent must carry at least one brown-eye allele. The other allele may be brown or blue. One way to assess this is to look at that parent's own parents, the future grandparents. If either grandparent has blue eyes, the brown-eyed parent also carries a blue-eye allele. The baby may inherit either allele, giving a 50% chance of blue eyes. (Case 3) If both grandparents have brown eyes, prediction is harder. Their siblings' eye colours may provide clues: a blue-eyed sibling indicates a blue-eye allele in the family. If both alleles in the brown-eyed parent are brown, the baby will carry a blue-eye allele in its genes after inheriting one from the blue-eyed parent. (Case 2)

If both parents have brown eyes
Each parent may carry two brown-eye alleles or one brown and one blue allele. If both have two brown alleles, the baby cannot have blue eyes. If one has two brown alleles and the other has one brown and one blue, the baby may inherit blue but will have brown eyes because brown is dominant. For blue eyes, both parents must carry a brown and a blue allele, and the baby must inherit the blue allele from each. The chance of blue eyes for each baby is then 25%. (Case 4)