Zygotic splitting occurs between days two and six when the zygote divides, usually into two, and each zygote then goes on to develop into an embryo, leading to identical twins (or triplets if it divides into three). These are known as "monozygotic" twins (or triplets).

What day does egg split for twins?

In 5% of the MZT cases, the splitting occurs 8-13 days after fertilization, resulting in monochorionic-monoamniotic twins (one placenta and one amniotic sac). Rarely, the splitting occurs after 13 days, resulting in conjoined twins.

What Week Do twins separate?

The American College of Obstetricians and Gynecologists (ACOG), for example, recommends delivery between 34 and 37 weeks for twins with a shared placenta and at 38 weeks for twins with separate placentas. Some other physician groups recommend delivery closer to 39 weeks with separate placentas.