When an egg is fertilized by a sperm cell, the cells begin to divide and develop, forming the embryo, which subsequently becomes the fetus. During an in vitro fertilization cycle, it is not uncommon for several embryos to form. In most cases, since only one embryo will be transferred into the uterus, it is necessary to freeze any extra embryos that form. These are called supernumerary embryos. By freezing them, patients can attempt IVF again in the event their cycle fails, or plan for a second pregnancy later on.
We may also recommend freezing embryos during an IVF cycle, if medical conditions are not favourable for an embryo transfer. This precaution is often taken to ensure the embryo is transferred under the best possible conditions, in order to maximize the chances of success.