Blastocyst culture and transfer
The Herts & Essex Fertility Centre has one of the largest blastocyst transfer programmes in the UK. We have excellent success rates 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 developed in the laboratory for five days after insemination. Blastocysts have a large, central, fluid-filled cavity and two distinct cell types.
The cells 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 forms the trophectoderm and will give rise to the placenta.
Until recently, successfully culturing embryos to the blastocyst stage was difficult. Initially, only 17% of embryos reached the blastocyst stage and pregnancy rates using blastocysts were only 10%. Scientific advances have led to the development of culture media that mimic the changing environment of the reproductive tract and meet the unique requirements of the embryo as it travels through the fallopian tubes. Our blastocyst formation rate averages at 65% of embryos to successfully grow to the blastocyst stage in the laboratory environment.
What are the advantages of blastocyst culture?
The appearance of an embryo is not always capable of predicting blastocyst formation or implantation potential. On average, only 15-20% of 2-4 cell embryos transferred to the uterus will implant. Blastocysts, in comparison, have an implantation potential of up to 60% per blastocyst. The ability to transfer a single blastocyst with a high implantation rate as opposed to Day 2 or Day 3 embryos, will increase the chance of a healthy singleton pregnancy and reduce the incidence of multiple births with the associated risks.
Why is blastocyst culture so successful?
Blastocyst transfer mimics natural conception in which the embryo travels down the fallopian tube and reaches the uterine cavity five days after fertilisation. This synchronises the development of the embryo and the lining of the womb to increase the chance of implantation.
Blastocyst culture exerts a selection pressure on a group of embryos and only the strongest and fittest will develop successfully to the blastocyst stage. By selectively excluding slow and arrested embryos from transfer, blastocyst culture will increase the probability of transferring a genetically normal embryo with a high implantation potential. This will increase the chance of achieving a successful pregnancy.
Can everyone have a blastocyst transfer?
Blastocyst transfer is not suitable for everyone. It is a laboratory 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.
Not all embryos are happy in the laboratory environment and for this reason you may benefit from a transfer on Day 2 or 3. If your embryos’ development is a little bit slow or if it is already clear which embryo is the strongest for transfer, the embryology team will recommend a Day 2 or Day 3 transfer. It is important not to feel disheartened as there is still a good chance of a successful pregnancy following a transfer on Day 2 or Day 3.
Our experience with blastocyst culture and transfer
Our blastocyst culture programme began in 2000. We initially concentrated on patients with a history of repeated failed attempts but with 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 are assessed by an embryologist who will guide and discuss with you the best day for your embryos to be transferred.
What are the disadvantages of blastocyst transfer?
The greatest disadvantage 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. It is fair to say that if an embryo does not survive to the blastocyst stage outside the uterus, it’s highly unlikely that it would have done so if transferred on Day 2 or 3.
Is there any extra cost for blastocyst transfer?
There is an additional fee of £450 for blastocyst culture which is charged separately. This is refundable if you have a Day 2 or Day 3 transfer and there are no remaining embryos for culture to Day 5.