The Herts & Essex Fertility Centre has one of the largest Blastocyst Transfer Programmes in the UK. We have produced excellent results and the programme has been widely acclaimed by professional colleagues in the field of embryology
What is a Blastocyst?
A blastocyst is an embryo that has been allowed to develop in the laboratory for five days after insemination. Blastocysts are characterised by a large central fluid filled cavity and two distinct cell types. The cell in the centre of the blastocyst is called the inner cell mass and will give rise to the foetus following implantation. The single layer of cells on the outside of the blastocyst, called the trophectoderm, will give rise to the placenta.
Until recently, successfully culturing embryos to the blastocyst stage in the laboratory was difficult. Initially only 17% of embryos reached the blastocyst stage and pregnancy rates using blastocysts were only 10%. Advances in science however have led to the development of culture media that can mimic the changing environment of the reproductive tract and meet the unique requirements of the embryo as it travels from the fallopian tubes. This allows embryos to successfully grow to the blastocyst stage in a laboratory environment.
What Are the Advantages of Blastocyst Culture?
Statistics demonstrate that only 15-20% of 2-4 cell embryos transferred to the uterus will implant. In contrast blastocysts have implantation potential of up to 60% per blastocyst. The ability to transfer a single blastocyst with a high implantation rate as opposed to multiple 2-4 cell embryos with a low implantation rate helps to reduce the incidence of a multiple birth and its associated risks. For more information on these risks see the page on multiple births.
Why is Blastocyst Culture so successful?
Blastocyst culture mimics natural conception. In a normal pregnancy the embryo travels down the fallopian tube and reaches the uterine cavity five days after fertilisation. This synchronises the development of the embryo with the development of the endometrial lining.
In blastocyst culture only the strongest and fittest embryos will develop to the blastocyst stage. By selectively excluding slow and arrested embryos from transfer, extending the culture period to five days will increase the probability of transferring a genetically normal embryo with high implantation potential and thus increase the probability of a pregnancy.
Why Can’t Everybody Have a Blastocyst Transfer?
Blastocyst transfer is not suitable for everyone. It is a selection process to identify the best embryo. In patients with only 1 or 2 embryos the embryos have already selected themselves for transfer and there is no significant advantage to leaving them outside of the uterus for longer.
Our Experience with Blastocyst Culture and Transfer
Our blastocyst culture programme began in 2000. We initially concentrated on those patients with a history of repeated failed attempts and who had a good number of embryos. The results were very encouraging and our first blastocyst babies were delivered in June 2001.
Today we offer blastocyst transfer to any patient who has a sufficient number of good quality embryos on day 3 after fertilisation. The developmental stage and quality of the embryos is assessed by an embryologist. They will advise you whether it is better to transfer the embryos on days 2 or 3 or extend the culture of your embryos until day 5.
If blastocyst culture is not possible and a day 2 or 3 transfer is advised there is still a good chance of success. If you have any remaining embryos following your transfer they will be cultured to the blastocyst stage and their suitability for freezing assessed.
Is There Any Extra Cost For Blastocyst Transfer?
No, there is no additional charge for culturing the embryo to the blastocyst stage.
Are There Any Disadvantages to Blastocyst Transfer?
The greatest risk is that there is a 2% chance that none of the embryos will continue to develop and form blastocysts by day 5. This is because not every embryo has the capability of forming a blastocyst. Not all of them are able to activate their genetic machinery that allows them to grow between the cleavage stage and the blastocyst stage. However if none of the embryos make it to the blastocyst stage outside of the uterus it is highly unlikely that they would have done so had they been transferred on day 2 or 3. This is why we are cautious about identifying patients who will benefit from blastocyst culture.