Nashville Fertility

Stages of Embryo Development

Learn more about the stages of embryo development and why they matter

Learn more about the stages of embryo development and why they matterEmbryologists closely monitor embryos during the stages of embryo development. An embryo begins to develop after sperm fertilizes the egg. It then takes about five days to become a blastocyst. The transfer of an embryo into the uterus of the hopeful mother or the gestational surrogate occurs after the embryo reaches a certain stage of development. Timing matters because it helps increase the likelihood that the embryo will lead to a healthy pregnancy.

Diving deeper into the stages of embryo development

After fertilizing the egg with sperm, the embryologist places the developing embryos into an incubator that mimics a woman’s body. The embryologist then monitors the embryos during development. They will give each embryo a grade depending on how it’s developing. Here is a basic overview of the stages of embryo development.

Zygote. After the sperm fertilizes the egg, it develops into a zygote. A zygote is a single cell containing a nucleus made of chromosomes from a male and a female.

Cleavage. The cleavage stage of development, which occurs on Day 3, involves the single cell zygote splitting and becoming an organism with about eight cells through the process of mitosis.

Compaction and differentiation. On Day 4, the cells in the developing embryo continue to split and the shape of the embryo changes. During this time, the cells come into close contact, form a tighter structure and become visible. Differentiation also occurs, which is when the simple cells of the embryo transform into more complex cells.

Blastocyst. By Day 5 or 6, the embryo is a blastocyst. A blastocyst is a cluster of rapidly dividing cells.

The specialists at our Tennessee fertility clinic help patients further understand the stages of embryo development during an IVF cycle.

What stage of embryo development is ideal for transfer?

The doctors at our Tennessee fertility clinic typically transfer embryos on Day 5 of development, when they are a blastocyst. Day 0 is the egg retrieval. Most embryo transfers occur on Day 5 because it allows the fertility specialist to select the highest quality embryo for transfer.

The highly qualified embryologists at our clinic carefully monitor embryos during the stages of development to help ensure they have the best chance of resulting in a healthy pregnancy. Contact us for more information about embryo development.


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