After ovarian stimulation and egg pick-up, there are often some extra embryos left. If these are healthy-looking, they may be frozen. By freezing these embryos, you have the chance to attempt pregnancy again at a later date. As the embryos have already been formed, no further injections or operative procedure to remove the eggs is necessary. We just have to place the embryos back in the uterus at the right time of the month when the uterus is most fertile. Note that not all unused embryos are suitable for freezing.