What are the causes of Multiple Pregnancy?

"In monozygotic twins what happens is when the zygote keeps on dividing, at one particular stage, the single zygote divides completely into two and each one develops into a separate embryo. That is why it is called as a monozygotic twins. Monozygotic twins genetically they are similar and they share the same blood group and they will be of the same sex. In monozygotic twins what happens is the zygote divides completely into two and each one develops into separate baby. So what happens is in monozygotic twins, they will be of the same sex and they will be of the same blood group and they will be of the same genetic composition. Depending on the stage at which this complete division happens. We call it as diamniotic, dichorionic, monozygotic twins or monoamniotic, monochorionic and monozygotic twins and especially if the division is incomplete, bit the babies may be fused at different levels of the body and that is what we call it as conjoined twins"