From the initial fertilization of eggs to the formation of blastocysts in the laboratory, each embryo stage plays a role in determining the viability and potential success of embryos. This knowledge allows you to make informed decisions about embryo selection, timing of transfer and overall pregnancy expectations.
By comprehending these developmental milestones, you can better navigate your IVF journey, ensuring that every step aligns with your goals of achieving a healthy surrogate pregnancy and fulfilling your dreams of parenthood through surrogacy.
To learn more about how you can get a head-start on surrogacy during the embryo development stages discussed below, fill out our contact form.
Preparing ahead of time means that your journey can continue seamlessly once you're ready to move forward. Whether that is creating your intended parent profile to help you find a surrogate or finding a fertility clinic where you will create your embryos, we’re here for you.
What Are the 5 Stages of IVF?
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Step 1: Medication
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Step 2: Egg retrieval
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Step 3: Fertilization
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Step 4: Embryo culture
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Step 5: Embryo transfer
What Are the Stages of Embryo Development?
The developing embryo stages are crucial to tracking the maturity of the eggs and knowing when the time is best to transfer them.
These embryo stages can be broken down day by day starting with fertilization and how the cells will look in the first few days to the fifth day when they can be biopsied for PGT before an embryo transfer.
Here’s a breakdown of what’s happening during the embryo development stages:
Embryo Stages Days 1-3: Cleavage
The first few days after fertilization are called the cleavage stage. The cleavage stage sees a multicellular organism begin to form through mitosis, where cells divide equally and replicated chromosomes form two new nuclei.
On the first day after egg retrieval, around 16-18 hours after insemination, the eggs are evaluated to see if they’ve become fertilized.
Normally fertilized embryos have two nuclei, one from the egg and one from the sperm. These fertilized eggs are incubated, mimicking the tubal fluid found in the body.
On day two, cell division is evaluated with the majority of them being either 2 cell embryos or 4 cell embryos by this point.
At this point, if an embryo hasn’t divided, it’s deemed not suitable for transfer.
Embryology will determine if a day three or day five transfer is the best for your situation, based on the number of available embryos as well as the quality of cell division in those embryos.
By the third day, embryos will have developed to between six and 8 cell embryos. Your embryo can take place on this day if conditions are optimal and assisted hatching is often used to help an embryo implant.
Assisted hatching is a procedure that thins or makes a hole in the protein layer surrounding an embryo.
Embryo Stages Days 3-5: Morula
The third day is also when a biopsy for pre-implantation genetic diagnosis (PGD) can take place. PGD sees the removal of one or two cells to be evaluated for specific genetic conditions.
Unaffected embryos are then transferred back to the surrogate’s uterus on the last day of the morula stage.
Days 3-5 are called the morula stage because the fourth day of embryo growth sees the cell compact, developing into a 16 cell embryo.
The morula itself is the cluster of cells that is formed after fertilization and before the blastocyst stage.
On the fifth day, you can grade the embryo on its:
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Inner cell mass (ICM): The ICM consists of cells within the blastocyst that will eventually develop into the fetus.
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Trophectoderm cells (TE): The trophectoderm plays a crucial role in early embryo development by forming the outer layer of the blastocyst that will become the placenta.
Embryo Stages Days 5-6: Blastocyst
On the fifth day, the blastocyst forms. A blastocyst is a cluster of dividing cells from a fertilized egg.
The layers of these cells divide and separate, eventually becoming the structures that help protect and nourish a fetus.
Day five is a common time for embryo transfers to take place and if any viable embryos are not transferred, they are typically frozen for possible later use.
These frozen embryos can be transferred the next day, but if they are not, they must be frozen. The sixth day is the last day that an embryo can remain in a lab without being transferred or frozen.
What Is the Best Grade of Embryos in IVF?
The best grade of embryos in IVF is typically ranked using a number or letter system. In IVF, the grading of embryos is based on various factors such as the number of cells, cell symmetry and degree of fragmentation.
The best grade of embryos typically includes those with characteristics indicating optimal developmental potential.
Grading embryos comes down to the system of the clinic conducting the grading. High-grade embryos have cells that are similar in size with less than 20% loss of cytoplasmic content.
Contact us online to get more free information about your surrogacy journey.
We can walk you through filling out your surrogacy planning questionnaire, getting you active and helping make your intended parent profile so that once your embryos have completed these developmental stages, your journey to parenthood can continue without any stops.