How long do embryos take to develop?
The day after the sperm is mixed with the egg, embryologists will look for signs of fertilisation. The following day they will check to see if the embryo has cleaved. Embryos can be transferred at any stage from day 2 up to day 6. By day 5 or 6, the embryos should reach the blastocyst stage.
The embryologists monitor and grade the embryos very carefully. In the majority of cases, if the embryos have developed well we would recommend a single embryo to be transferred to reduce the risk of twins.