In-vitro Fertilization (IVF) refers to a technique of assisted reproduction where the egg and sperm are fertilised outside of the body to form an embryo. This embryo is then transferred to the uterus to hopefully implant and become a pregnancy. All IVF treatments begin with a course of hormone therapy to stimulate the development of several follicles in the ovary. These are collected as eggs, which are then fertilized in a test-tube (‘in-vitro’) to create several embryos. After two to five days in an incubator, one or two of these embryos are transferred to the uterus, where implantation occurs and pregnancy begins. However, in IVF as in natural conception, not every embryo implants to become a pregnancy, which is why surplus embryos are frozen – so that a subsequent transfer might be tried if the first one fails.