Are the implantation rates of frozen blastocysts better?

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Traditionally, better results were obtained with embryo transfers in fresh than with frozen ones. However, nowadays, thanks to advances in the field of assisted reproduction, better success rates are achieved with the transfer of vitrified blastocysts. In this article we will see what is due.

Below you have an index with all the points that we will discuss in this article.

Index

Are implantation rates of frozen blastocysts better?

Transfer of frozen embryos

In a natural menstrual cycle, the most common is that it only matures and an ovule is released with ovulation. Therefore, in in vitro fertilization (IVF) treatments, hormonal stimulation is performed in order to obtain a greater number of ovules.

Although in this way it is possible to increase the chances of success of these techniques, the stimulation also has detrimental effects on the endometrium (the layer that covers the surface of the uterine cavity), which negatively affects the embryo implantation in the fresh cycles.

Therefore, the endometrium is more receptive in the transfers of frozen embryos than in those of the fresh cycles, since it has had a whole menstrual cycle to recover from the effects of hormonal stimulation.

Hormone stimulation affects endometrial quality

Until recently, slow freezing was the method used to cryopreserve embryos left over from assisted reproduction treatments and the results obtained were limited.

In recent years, the technique of vitrification has been implemented, which consists of freezing embryos in an ultra-fast manner. Through this procedure, very high survival rates (90-95%) are achieved because the damage suffered by embryos in the freezing process is minimized.

Therefore, these advances in cryopreservation allow vitrifying embryos without compromising success rates and even improving them.

Why transfer in blastocyst stage?

Advances in assisted reproduction techniques have also made it possible to considerably improve the embryo culture, that is, the conditions in which the embryos are in the laboratory until they are transferred or vitrified. This has made it possible to get more embryos of good quality and to reach the blastocyst stage.

The blastocyst stage is reached on day 5-6 of development.

The transfer in this stage presents a series of advantages:

  • It allows for a better embryonic selection, since more development information is obtained and only those with the best quality are able to reach this stage.
  • There is a better synchronization with the endometrium, which increases the chances of implantation.
  • More transfers can be made from a single embryo to avoid multiple pregnancies without compromising the chances of success due to the two previous points.

Risks

Although the transfer of vitrified blastocysts can provide very good implantation rates, it is not always the best option.

On the one hand, it is important that the vitrification protocol is optimized so that very good results are obtained. The blastocysts contain a lot of water inside and this makes the freezing process difficult, so if you do not have a good cryopreservation program, you will get worse results than fresh.

In addition, we must bear in mind that not all embryos reach this stage: only those that are of good quality. Therefore, the risk that no embryo reaches this stage should be assessed.

Only good quality embryos reach the blastocyst stage

Therefore, the transfer of vitrified blastocysts should not be performed in all patients, but should only be indicated in those who may benefit from this therapeutic option.

Questions from users

Is any endometrial preparation treatment necessary before carrying out the transfer of frozen embryos?

Transfers of frozen embryos can be made in either a natural or a substituted cycle. In the case of the natural cycle, the natural hormones of the patient's menstrual cycle are used and the evolution of the follicle and endometrium is controlled by ultrasound, without administering any medication. Once ovulation has occurred (release of the mature ovum), treatment with progesterone is initiated.

In the substituted cycles, estrogens are administered to prepare the endometrium, either in the form of patches or pills. When it is observed by ultrasound that the endometrium is ready, progesterone is administered.

You can benefit from our discounts to perform these treatments by visiting the following link: Discounts in assisted reproduction clinics.

It will be done in one way or another depending on the characteristics of each patient: if you have a menstrual cycle, results of previous cycles ... In addition, there may also be variations in these treatment guidelines that we have discussed, such as administering GnRH analogues, for example .

Are the symptoms of frozen blastocyst transfer the same as if they are fresh?

Yes, since there are no differences between the two transfers, the procedure is the same. The only thing that can vary is that in the fresh transfer remain symptoms of hormonal stimulation.

Can an embryo that has been thawed be frozen again?

Yes, as long as the vitrification and devitrification are carried out correctly, an embryo can survive several cycles of freezing without compromising its viability and being able to carry out the implantation.

Recommended reading

As we have said, the transfer of frozen embryos is very similar to that of fresh embryos. If you want to know in detail all the steps of this procedure, we recommend that you visit the following link: Transfer of frozen embryos.

On the other hand, one of the most relevant decisions of IVF treatments is if the transfer is made on day 3 or in the blastocyst stage. To know the advantages and disadvantages of each of these options, you can read the following article: Embryo transfer on day 3 or on day 5?


preimplantation genetic diagnosis in Madrid(Spain)

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