The embryo is the origin of the future baby that is develops inside the womb. It is a living organism and, in its development, it goes through different stages until it finally becomes a fetus. Let’s see what those stages are.

First stage.

On the first day of embryo development, experts at Procreatec can already detect whether fertilization through assisted reproduction techniques has been successful. How is it possible to identify a fertilized egg correctly? The egg must have two polar bodies and two pronuclei. The polar bodies are cells that contain the excess material of the oocyte. As for the pronuclei, one of them includes the genetic material of the mother and another of the father.

Second stage.

On day 2, the first and second cell divisions take place. A healthy embryo has four formed cells at this stage. Cell division is an essential stage in the development of the embryo because it allows the organism in gestation to grow and develop.

Third stage.

On day 3, the embryo must have been divided into 8 cells and have begun to use its own genetic material. At this stage, the Procreatec specialists begin to analyse fundamental characteristics of the cells to assess their quality: symmetry, number of nuclei and fragmentation. The best cell is the one with a single nucleus.

Fourth stage.

This phase is called “the morula stage”. Morula refers to the mass of cells that have originated as a consequence of the division of the initial cell. Its name is due to the fact that this mass has a shape similar to that of a blackberry (“morula” in Latin). At this stage, it is not possible to differentiate the cells. It is an intermediate phase between the initial cell or zygote and the blastocyst.

Fifth stage.

This stage consists of days 5 and 6 of the embryo development. At this stage, specialists can already recognize the outer layer of the embryo (trophectoderm), from which the placenta will develop, as well as the internal cells that will form the baby. This phase is called blastocyst. It is the last stage of the embryo before its implantation in the uterus. In this last sequence, the embryo has a complex cellular structure formed by around 200 cells.

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Pioneers in embryo transfer at blastocyst stage

At Procreatec, we are pioneers in embryo transfer at blastocyst stage. This phase is the best at which to carry out the transfer of a single embryo, as it significantly increases the chances of successful implantation.

Through sequential blastocyst culture, it is possible to achieve an embryo on day 5 with a developed and complex cellular structure. The selected embryos are the ones that present the best qualities.

We recommend the transfer of one embryo at blastocyst stage to patients with a high number of good quality embryos after egg donation or a cycle of In Vitro Fertilization, as well as to women who have not achieved pregnancies after several transfers on the third day of embryo development. An added advantage of this culture is that it avoids multiple pregnancies and the medical complications that this could bring to the mother. In addition, more and more, women over 40 who undergo treatment using donated eggs take advantage of this special technique.

If you have any questions about the culture to blastocyst, do not hesitate to ask for a free appointment or ask us to call you. You can reach us at or by phone 0034914585804.

About the author


At ProcreaTec, we understand the road toward a healthy pregnancy is not always easy. Through this blog, we want to reach out to all who are struggling on the path of infertility to find support. If you have any questions or would like to tell us about your situation, you can comment on the posts or send us an e-mail.
If you would like to learn more about our clinic, we invite you to visit our website
ProcreaTec: converting patients into parents.

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