A blastocyst is an embryo which has developed to the 5-day stage. If an embryo reaches this stage in the laboratory, the chances of pregnancy are higher and the risk of multiple births is reduced. Blastocyst culture is useful when a patient has a large number of high-quality embryos three days after insemination, because it allows the embryos to develop further and makes it easier for the embryologist to pick the blastocyst with the best potential. But not all embryos survive to develop into blastocysts and so a potential risk is that no blastocysts may develop. Whether blastocyst transfer will benefit a particular patient is decided once the embryos have been graded. Any leftover blastocysts can also be frozen for future use.

The period of extended culture helps our experts select the most competent embryo(s) for transfer to your womb, and can help to indicate which embryos have the best growth potential. Therefore, blastocyst culture maximises the chance of you achieving a viable pregnancy.

By the time an embryo has reached the blastocyst stage, it’s already undergone several cell divisions and achieved its first cell differentiation into two distinct cell types.

To be eligible for blastocyst culture, patients need to have a good number of embryos (ideally more than four) that are at the right stage of development on Day Three. Once these criteria have been met, extended culture may be offered as a possible option.