In natural conception embryos arrive in the uterus 5-6 days after fertilisation. With present day IVF, embryos are routinely transferred back 3 days after fertilisation. Recent breakthroughs in the laboratory and developments in media culture have made it possible to grow embryos in vitro for up to 5 days. This is referred to as blastocyst development.

By growing the embryos to blastocyst stage you have the potential to choose the best developing embryos and also to transfer fewer embryos, which results in increased pregnancy rates and lowers the multiple pregnancy rates.

However, not all patients are suitable candidates for this procedure.