The Herts & Essex Fertility Centre has a well established Blastocyst Transfer Programme that has been widely acclaimed by professional colleagues in the field of embryology. We have one of the largest blastocyst programmes in the UK, yielding excellent results.
What is a blastocyst?
A blastocyst is an embryo that has been allowed to develop in the laboratory for five days or more after egg collection rather than two to three days in the laboratory before being transferred into the uterus. Until fairly recently, culturing embryos successfully in the laboratory to blastocyst stage, and at the same time achieving a good pregnancy rate, was extremely difficult. Research has shown that an embryo has different needs during various stages of development. In response to these needs, scientific progress has led to the production of innovative sequential culture media, enabling embryos to grow and survive under laboratory conditions to the blastocyst stage.
What are the advantages of blastocyst culture?
Worldwide statistics show that of all 2-4 cell embryos replaced in the uterus, only 15-20% actually implant. Blastocysts, on the other hand, are up to three times more likely to implant than two or three day old embryos. Implantation rates in excess of 60% per blastocyst are regularly achieved. It is now possible to transfer a single blastocyst in patients and still achieve success rates comparable to the transfer of two embryos on day 2-3.
Why is blastocyst culture so successful?
There are a number of possible reasons for its success. The most likely reason is that embryos which develop successfully to the blastocyst stage are undoubtedly fitter and stronger, with a greater potential to implant. Blastocyst transfer is more physiological as it mimics natural conception whereby the embryo travels down the fallopian tube and reaches the uterine cavity five days after fertilisation. This ensures correct synchronisation between embryo and uterine lining development.
If so successful, why can’t everybody have blastocyst transfer?
Unfortunately, not many embryos survive to five days in the laboratory and, if not carefully selected and monitored, some patients would not make it to the blastocyst transfer stage. It is important, therefore, that we select patients who on day three have at least three good quality embryos. If the number of embryos is low there may be no significant advantage to leaving the embryos outside the uterus, as we already know which embryos are to be selected for transfer.
Our experience with blastocyst culture and transfer.
Our blastocyst culture programme was started in 2000. We have concentrated on those patients with a history of repeated failed attempts through standard IVF, but who always generated a good number of embryos. The results were very encouraging and our first blastocyst babies were delivered in June 2001.
We offer blastocyst culture to any patient who has a sufficient number of good quality embryos on day 3. The embryos are assessed each day after egg collection and the patients are informed accordingly of their progress. If the embryo quality is poor or if there are less than three good quality embryos, they will be transferred on Day 2 or Day 3 as there is no benefit in leaving them in the incubator. Culturing embryos to blastocyst stage will be suggested if by Day 3 there are at least three good quality embryos.
If blastocyst culture is not possible and a Day 3 transfer is advised, there is still a good chance of success. In fact, the success rate of patients who are recalled for a day three transfer instead of proceeding to blastocyst culture, is as good as for standard IVF.
Are there any disadvantages associated with blastocyst transfer?
As mentioned before there is a possibility that none of the embryos may survive to Day 5. Generally, we tend to be extra cautious by recalling patients on Day 3 for embryo transfer if we have the slightest doubt as to the further development of the embryos.