twin pregnancy

As if having a single child developing inside you isn't enough, twin pregnancy does happen. As many will know, twins can be either identical or non-identical. In identical twins, the two babies are obviously the same sex, while in non-identical twins, the two babies can be different sex.

Non-identical twin pregnancy occus when two of the mothers eggs are fertilized by two separate sperms of the father. That way, two embryos form and embed in the mothers uterus. The two children are genetically different as any other brothers or sisters will be.

Identical twin pregnancy occurs when a single egg from the mother is fertilized by a single sperm from the father. This results in a single ball of cells forming which would make a single baby. However, at some point in the early division of cells, the ball splits into two parts. Each part contains the exact same genetic material as the other and both have the capability of becoming a baby. Since both of the developing babies received the exact same genetic information from the egg and sperm as each other, both babies are identical. Identical twin pregnancies are not common but they do happen.

When two childen are born from an identical twin pregnancy, it is possible for each to have small distinguishing marks on their bodies that are obviously not the results of the identical genetic material they both started off with. These marks would be due to mutations in the DNA (very common and normal in all of us) at some point after the ball of cells split into two. The results is slight changes in the DNA and occasionally these changes do show in the outward appearance.