Blastocyst Culture and Transfer
You may be aware from press releases and other information sources that one of the new techniques in an IVF Laboratory to help treat infertility is blastocyst culture and transfer. For some patients, blastocyst culture offers an alternative method to achieve a pregnancy following embryo transfer.
What is blastocyst culture?
Blastocyst culture is a laboratory technique in which embryos grow in the laboratory for 5 to 6 days as compared to the current 2 to 3 days. This extended culture period allows viable embryos to continue development and reach the blastocyst stage of embryo development. The development of nutritive solutions to support embryo growth has greatly improved in the last few years and has led to the clinical application of this technique. The blastocyst stage embryo is still effectively a ball of cells approximately 100-150 cells in total (see Figure 1). In terms of size, the embryo isn`t much bigger than what it was at day 2 or 3, somewhere around 1/5 millimetre. Blastocyst stage embryos are transferred to the uterus on day 5 or 6, instead of day 2 and 3 following egg collection.
What is the advantage of blastocyst culture?
When blastocyst culture is performed and two blastocyst stage embryos are transferred, our preliminary results and overseas data shows that the overall pregnancy rate for all patients increases from 25-30% (for day 2 and 3 embryos) to 50% (day 5 to 6 embryos). This is because the embryo(s) being transferred have been developmentally tested in the laboratory. The fact that these embryos have reached the blastocyst stage in the laboratory implies they are better at developing than the embryos that fail to reach this stage. However, even with successful blastocyst culture, there is still a chance that a pregnancy may never occur, because of other problems.
What are the disadvantages of blastocyst culture and transfer?
With blastocyst culture there is a much greater risk that you will not receive any embryos to transfer, as none will reach the blastocyst stage. About 1/3rd of all patients who begin blastocyst culture won`t have an embryo that reaches the blastocyst stage and therefore will not have an embryo transfer. To minimize the risk of this, the laboratory will monitor your embryos and if in our opinion we should not continue with extended culture, we will offer you an earlier embryo transfer. There is also a substantially greater risk of having twins if you have 2 blastocysts transferred, plus an increased risk of monozygotic (identical) twins as well. Therefore, you need to discuss with your Repromed doctor how many embryos to have transferred.
As with embryo transfer on day 2 or 3, any remaining embryos that are suitable are frozen and stored for later transfer. However, because fewer embryos grow to the blastocyst stage, there are fewer embryos remaining that can be stored. In addition, survival following thawing and pregnancy rates for frozen/thawed blastocysts is poorer than for fresh blastocysts, and is comparable to day 2 and 3 embryos (around 15-20%). Because fewer embryos grow to the blastocyst stage and the pregnancy rate following embryo storage is the same as for day 2/3 embryos, your overall chances of getting pregnant from all embryos produced during a treatment cycle is no different if you opt for blastocyst culture.
Who is blastocyst culture suitable for?
- have had 3 or more stimulation cycles and are still not pregnant.
- are 40 years of age or older.
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should only receive a single embryo at transfer, to minimize the risk of multiple pregnancies.
- have many embryos already in storage.
Blastocyst culture won`t suit everyone. However, we think it may be an option for you to consider with your Repromed doctor if you: