How The occurrence of twins?

 Twins (Identical)

 

Identical twins are also called twin Monozygotik, the twins come from one egg. Have the same genes, same sex, and face similar.
The process of identical twinning is due at the time of fertilization of an egg is cooked in buahi by a sperm which form a zygote, then this zygote will divide.
If cleavage occurs when the zygote is the beginning of fertilization (1-3 days after fertilization), each embryo will usually have different amniotic sack, and one placenta.
But when the division occurred after 14 days then chances are there will be twins join / stick together on the part of the body or cleavage is not perfect so-called Siamese twins higher.
So the twins conjoined twins occur in monozygot. With ultrasound examination (utrasonografi) the doctor will be able to assess the state of the fetus, gender, and position defects etc..

Twin Dizygotik

 

Fraternal twins are also called twin dizygotik, the twins who came from two eggs. They usually are not too similar or just like brothers
Do not always have the same sex in which: 1 / 2 part of the fraternal twins are boys - girls; fourth part is the boys - and boys; 1 / 4 part again girls - girls.
The process of occurrence of fraternal twins, that is because at the time of conception there are two mature egg cells, each of which has been filled by a different sperm.
Coming from two different eggs and sperm, each has its own amniotic sac and placenta. So fraternal twins, are the 2 processes of fertilization in a single pregnancy.
Approximately 2 / 3 part of the twins are fraternal twins. Usually the doctor will be able to express identical or fraternal twins after the birth process with rate of placenta.