In conventional IVF, the embryo transfer was done in the uterus after 48 hours at 4-8 cell stage. In natural conception the embryo reaches the uterine cavity only on day 5. So embryos were put back at the wrong embryonic age at the wrong place and at the wrong time. With the availability of new extended culture medium, culture the embryos in the lab till the blastocyst stage (i.e day 5-6) can be done . Thereby increasing the chances of success dramatically to 50%.