What is a blastocyst transfer?

A blastocyst is an egg that has been fertilised and has become an embryo. It is used as part of the IVF or ICSI process. An egg is fertilised in the laboratory by an embryologist using either donor or a partner’s sperm. Immediately after fertilisation, the egg starts to divide and develop into an embryo. Around five days after fertilisation, the egg becomes a blastocyst. One or two blastocysts are then implanted into the uterus (womb) where a successful pregnancy will hopefully follow.

What are the advantages of a blastocyst transfer?

After fertilisation, the egg is left to develop in the laboratory for five days before it becomes a blastocyst. Eggs can be transferred at any point following fertilisation. However, because blastocyst embryos have been able to develop for longer in the lab, embryologists can select which ones are most likely to implant in the uterus. According to the Human Fertilisation and Embryology Authority (HEFA), only 20% to 30% of fertilised eggs will reach the blastocyst stage. If embryos do reach this stage, there is a higher chance of implantation and a successful pregnancy.

Is a blastocyst transfer for me?

Blastocyst transfer is not suitable for some women if the embryologist is concerned that only a very few or no embryos will survive to the blastocyst stage. Women who produce few normal eggs such as those that are older, or those that only have one or two embryos are often not suitable candidates for a blastocyst transfer. Those women will likely benefit from a day-3 transfer.

A blastocyst transfer is more likely to be recommended to young, healthy women who have a good chance of becoming pregnant.

Success rates of a blastocyst transfer

Compared to an embryo transfer at an early development stage (day 2 or 3 following fertilisation), the chances of a successful pregnancy following a blastocyst transfer are much higher. This is because the healthiest looking embryos that have developed well in the laboratory are transferred. HEFA provides information on success rates following a blastocyst transfer. In women aged up to 30, the chance of a successful pregnancy is between 45% and 50%. This reduces to a 35% – 40% chance in women aged 30- 39.

You are as likely to have a successful pregnancy following the transfer of one blastocyst as you are with two. Therefore, many clinics will recommend a single blastocyst transfer with the highest quality embryo selected.