Triplets are three children born in the same uterus during one pregnancy. Like twins, triplets and other higher order twins can be classified according to their zygosity or degree of genetic similarity. While triplets are most often fraternal, triplets can be identical.
How identical triplets are born. While many people are familiar with the terms “identical” and “fraternal” when describing twins and use them to describe the similarity of twins or triplets, these terms actually refer to how twins are formed in utero. Monozygotic or identical multipliers are formed from the same egg.
In identical twins, the fertilized egg divides in two. In the case of identical triplets, the egg may only divide once into three, or twice, resulting in three embryos with the same general DNA characteristics. Monozygotic triplets are always of the same sex, either all boys or all girls. Some monozygotic triplets are actually quadruplets in which one embryo has disappeared or been reabsorbed.