It is useful for assisted reproduction in humans. Large numbers of embryo are frozen in liquid nitrogen, if produced in good number and quality. These can be used in case of a failed first cycle.
In egg freezing, the eggs are extracted and frozen and then stored. The frozen eggs are used for fertilization when the woman is ready at a later period. The eggs are thawed and subsequently fertilized before transfer to uterus. The egg retrieval method here is similar to that used in vitro fertilization.Egg freezing is productive for women who are undergoing some medical treatment whence pregnancy is not possible. It is also for females who wish to retain ability to have children in later stage when they get married.