While monitoring your embryos is the job of the embryologists, knowing about the stages of embryo development day by day can help you follow along and confidently make decisions regarding your IVF and surrogacy journey.
Contact us today to learn more about the steps you can take leading up to the creation of your embryos. Completing steps before your embryos are created, like filling out your surrogacy planning questionnaire or building your intended parent profile, means less time waiting to become a parent once your embryos are created.
We will lay out what each day looks like for your embryo and its day by day development, from the importance of specific days to what comes next.
Embryo Development Day by Day [7-Day Timeline]
Day zero of this growth process is the retrieval day. Eggs are retrieved from your ovaries before being counted and assessed for their quality.
Once the eggs are fertilized with sperm from the intended father or donor, it’s about looking for the signs that signal the creation of fertilized eggs.
Once the embryo transfer is complete, it’s a waiting game as your embryo grows day by day. It can take 9-14 days to detect a pregnancy, and you have to wait two weeks after the transfer for a pregnancy test.
Here’s a breakdown of embryo day by day development:
Day 1 Embryo
Around 16-18 hours after insemination, your eggs are evaluated to see if the egg and sperm have joined. Embryos with the presence of two pronuclei, one from the egg and one from the sperm, are your first signs that they are fertilized.
These fertilized embryos, also called "zygotes" at this stage, are stored in an incubator and continually observed to help determine the most viable option for the embryo transfer.
Day 2 Embryo
This is an important day in your embryo’s day by day development because an embryologist can decide if a day three or five transfer is better for your situation.
The cells in any fertilized embryos divide over the first couple of days, from one cell to two, two cells to four and so on. A day two embryo would ideally have between 2-4 cells, and if an embryo hasn’t divided by this point, it’s qualified as non-viable
Day 3 Embryo [The Cleavage Stage]
Cell division continues on day three, typically consisting of six or eight cells by this point. The genetics of the egg are pushing the development of your embryos as implantation begins.
If a day three transfer is part of your journey, then an embryo biopsy for the pre-implantation genetic testing (PGT) is often done to determine which embryos may be predisposed to chromosomal abnormalities or single gene mutations that may affect chances of pregnancy or result in passing on genetic disorders to your child.
If you are not having your transfer until day five, then your embryos are placed into an incubator that can mimic the uterine fluid from the body and a laser-induced “coin slot” is created in the outer shell of the embryo.
This indentation is a form of assisted hatching, which helps embryos break free of the outer layer of cells that protect an embryo when they are transferred.
Day 4 Embryo
At this stage of your embryo’s day by day growth, development continues as the cells begin to compact into a ball called a morula.
While the genetics from the egg have driven development to this point, day four sees the genetics from the sperm take action. The integration of the genetics from the sperm continues to advance embryonic development.
Many embryos do not make the multi-day transition from compacting cells to a morula. If the cells don’t compact on day four, blastocyst formation rates decrease.
Day 5 Embryo [Blastocyst Stage]
Day five is a significant milestone in an embryo’s development. This is what’s known as the blastocyst stage.
Day 5 blastocysts are considered optimal for your transfer in many cases because they have typically demonstrated good development and are more likely to implant successfully in the uterus.
Cell division has likely increased, resulting in roughly 120 cells. By day-5, embryos have undergone several rounds of cell division.
This cluster of cells will eventually develop into the fetus. This outer layer of cells will form the placenta and other supportive tissues. Two Main Components of a Blastocyst
A blastocyst is the early stage of an embryo and as fluid builds up in the embryo, it expands and enlarges.
Day 5 blastocysts are often assessed for quality and developmental stage before selection for transfer into the uterus. This assessment may include evaluating the size, shape and overall health of the blastocyst.
Embryos can be transferred through fresh embryo transfers on day five, with the option to wait untilday seven if waiting on genetic test results. If you decide to do a frozen embryo transfer (FET) you can have your embryos frozen and genetically tested.
We can connect you with a list of reputable fertility clinics near you.A clinic is needed to create your embryos
Day 6 Embryo
If not transferred or frozen already, the blastocyst continues to grow and mature, with further expansion of the blastocoel.
Non-viable embryos are discarded at this stage with it being the last day embryos can remain in a lab. If an embryo transfer doesn’t take place on day five, it must either be transferred or frozen on day six.
Day 7 Embryo
The blastocyst undergoes final preparations for implantation, including interaction with the endometrial lining of the uterus in preparation for pregnancy if it has already been transferred to your surrogate.
Delayed growth can result in some embryos not developing into a blastocyst until the seventh day. But an embryo that isn’t transferred to the uterus by the sixth day means it will be cryopreserved via vitrification.
Days 8-10 Embryo
Embryo development day by day from day 8-14 can be considered the steps of implantation. Days 8-10 are a continued part of the embryo’s growth as it hatches, develops and tries to attach itself to the uterus.
Days 11-14 Embryo
Implantation is typically completed, with the embryo securely attached to the endometrium. Three key steps of the implantation occur during days 11-14, these steps include:
When the blastocyst lands near the uterine wall and forms an initial, but loose connection. When the embryo attaches to the endometrium. When the outer cells of the blastocyst penetrate the uterine wall.
Once these key parts of the implantation process are complete, cells continue to divide into the two masses that become the fetus and the placenta.
Human chorionic gonadotrophin (hCG) is also released into the bloodstream, which can be an indicator of a pregnancy, and by days 11-14 may have high enough levels to detect a pregnancy through a blood test.
You’re probably eager to get started as you wait for your embryos. You can’t be matched with a surrogate until embryos with a high chance of success are created, but you can fill out our online contact form to get more free information about the necessary steps to become an active family with us.
As your embryo’s day by day development comes full circle, completing your surrogate planning questionnaire puts you that much closer to being able to experience parenthood.
FAQs About Embryo Development Day by Day
An average of 30-50% of fertilized eggs makes it to the blastocyst stage. Age, egg quality, embryo quality and your specific in-vitro fertilization cycle are all factors that impact the eggs that make it to this point in the process. The embryonic stage of a pregnancy usually lasts around five weeks, between the third and eighth weeks of your pregnancy. At the end of that eighth week, the embryo has taken on human characteristics and most organs have begun to take shape. Yes, although day five or six embryos are typically the standard for IVF laboratories, day seven embryos are OK. Some embryos grow slower than others and this can mean that some take until day seven to reach the blastocyst stage.
Glossary
Embryologists: Medical professionals who are responsible for the management and creation of viable embryos to be used in an IVF transfer or frozen for later use.
Pronuclei: The haploid nucleus of a male or female gamete, such as an egg or sperm, up to the time of fusion with another gamete in fertilization.
Zygotes: A fertilized egg cell that results from the union of egg and sperm from the male and female gametes.
Embryo Transfer: The final stage of the IVF process that involves the transfer of one or more embryos into the uterine cavity, usually by using a catheter inserted through the uterine cervix.
Pre-Implantation Genetic Testing: A screening test that can be performed on embryos created through IVF to genetically analyze the embryos prior to transfer.
Assisted Hatching: A procedure that helps the embryo “hatch” from its “shell” by creating a small crack in the zona pellucida.
Morula: A solid mass of blastomeres resulting from a number of cleavages of a zygote, or fertilized egg.
Blastocyst: A cluster of dividing cells made by a fertilized egg aka the early stage of an embryo.
Frozen Embryo Transfer: Thawing one or more embryos that were frozen during a previous treatment cycle and transferring that embryo(s) to the uterus in order to try to establish a pregnancy.
Vitrification: The process of freezing embryos so rapidly that that water molecules don’t have time to form ice crystals, and instead instantaneously solidify into a glass-like structure.
Fetus: A human in the later stages of development before it is born.
Placenta: A temporary organ that forms in your uterus during pregnancy. It attaches to your uterine wall and provides nutrients and oxygen to your baby through the umbilical cord.
Human Chorionic Gonadotropin: A hormone produced by the placenta during pregnancy. It helps thicken a person’s uterine lining to support a growing embryo and tells the body to stop menstruation.