
The process of identical twinning is due at the time of fertilization of a mature egg cell by a
sperm fertilization helps 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 the twins will probably happen 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 (utrasonografi) physicians will be able to assess the state of the fetus, gender, and position defects.