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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.
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What is a blastocyst?
A blastocyst is an embryo that has been allowed to develop in the laboratory for five days following the insemination of an egg with a single sperm. Blastocysts are characterised by a large central fluid filled cavity and two distinct cell types. The cells in the centre of the blastocyst are 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.
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Blastocyst culture
Until recently, culturing embryos successfully in the laboratory to the blastocyst stage was difficult. Initial blastocyst pregnancy rates were only 10% with as few as 17% of embryos reaching the blastocyst stage. Advances in science have led to the development of culture media that enables embryos to successfully grow in a laboratory environment to the blastocyst stage. This culture media can mimic the changing invitro environment of the reproductive tract and meet the unique requirements of the embryo as it travels from the fallopian tubes forming a blastocyst in the uterus.
What are the advantages of blastocyst culture?
The appearance of an embryo is not always capable of predicting blastocyst formation or implantation potential. Statistics demonstrate only 15-20% of 2-4 cell embryos transferred to the uterus will implant. In contrast blastocysts have an innately higher implantation potential of up to 60% per blastocyst. The ability to transfer a single blastocyst with a high implantation rate aims to promote SET (single embryo transfer) and reduce the incidence of a multiple birth and its associated risks.
Why is blastocyst culture so successful?
Blastocyst transfer mimics natural conception whereby 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.
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 extending the culture period will increase the probability of transferring a genetically normal embryo with a high implantation potential consequently increasing the probability of a pregnancy.
Why can’t everybody have blastocyst transfer?
Blastocyst transfer is not suitable for everyone. It is a selection process to identify the best embryo. In patients with one or two embryos the embryos have already selected themselves for transfer and there is no significant advantage to leaving the embryos outside the uterus.
Our experience with blastocyst culture and transfer
Our blastocyst culture programme started in 2000. We initially concentrated on those patients with a history of repeated failed attempts who had a good number of embryos. The results were very encouraging and our first blastocyst babies were delivered in June 2001.
We now offer blastocyst culture to any patient who has a sufficient number of good quality embryos on day 3. The developmental stage of the embryos and their quality is assessed by an embryologist who will advise you whether you would benefit from a transfer on day 2 /3 or extending 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 cryopreservation assessed.
Is there any extra cost involved for blastocyst transfer?
No, there is no an additional charge for blastocyst transfer.
Are there any disadvantages associated with blastocyst transfer?
The greatest risk is the possibility that none of the embryos continue to develop and form blastoysts on Day 5. There is a 2 % chance that there will not be any blastocysts on day 5. This is because not every embryo has the capability of forming a blastocyst. Not all embryos are able to activate their genetic machinery to allow them to grow between the cleavage stage and the blastocyst stage. If this happens it is highly unlikely these embryos would have formed blastocysts even if they had been transferred to the uterus on either day 2 or day 3. This is why we are cautious in identifying patients who will benefit from blastocyst culture.
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