One recognized demographic change over time has been the delay of childbearing - increasing numbers of women are delaying childbearing until their late thirties, or even their forties. However women who delay childbearing are at risk for infertility later on. All women grow less fertile over time. This occurs because women are born with a finite number of eggs (and don’t produce more) and over time this supply declines; also, egg quality declines naturally over time, so that individual eggs offer less chance of pregnancy and higher chance of pregnancy loss.
Women that hope to protect their fertility while delaying pregnancy, can now choose to cryopreserve (freeze) their eggs.
Women who elect to cryopreserve eggs undergo ovarian stimulation to provide the eggs that will be banked. Vitrified oocytes may be stored for years. When their use is desired, vitrified eggs are thawed, fertilized, and transferred as in routine IVF treatment.