At day 7 of embryo development in IVF, your embryo is likely transferred, and you may be getting excited about the possibility of pregnancy.
If you are creating embryos, our surrogacy professionals can help you plan for the next steps and get pregnant faster.
Read on to learn about the implantation and development that makes your embryo into your precious pregnancy.
To find out more about success rates, learn more here, or fill out our online form and get connected with a surrogacy professional.
What are Day 7 Embryos? [Blastocyst Development]
An embryo at 7 days looks similar to an embryo at day 5 or 6 of development. At approximately 1/100ths of an inch, it is less than 1/10th the size of a very fine grain of sand, but with magnification, fertility specialists are able to identify features like the inner cell mass, cell size and shape and cavitation, which can help them determine the quality of an embryo.
An embryo 7 days into development can be tested for things like genetic abnormalities, and if it was transferred to your surrogate, it was likely tested before transfer. An embryo usually “hatches” on day 6 or 7 after fertilization—a process that allows the embryo to implant and become a pregnancy. So on day 7, this may have already occurred, or it may occur soon. If the embryo was transferred before the embryo reached 7 days into development and the embryo has hatched, the embryo may already be beginning the process of implantation.
Are Day 7 Embryos Blastocysts?
Yes, a day 7 embryo is still considered a blastocyst. Around this point, the embryo will begin the implantation process.
How a Day 7 Embryo Develops After Transfer [The Two Week Wait]
If day 7 is the latest an embryo should be transferred, the next 14 days make up the “two week wait.” The implantation process occurs during the first 7-9 days after transfer.
While implantation may complete in that first week, and pregnancy may be detectable some clinics will wait 14 days after the transfer before they have your surrogate come in for a pregnancy blood test. During days 10-14 after transfer, the embryo continues to develop and hCG levels increase.
Here, we will break down embryo development in the days following transfer.
Days 1-6: Implantation Process
From the time that an embryo is transferred until the time it is fully implanted, a few things happen:
The embryo (now known as a blastocyst) hatches from its shell (known as the zona pellucida). If you transferred a day 7 embryo, it’s possible hatching already occurred before the transfer. This allows the embryo to attach to the uterine lining. The blastocyst sends out molecular signals to find a hospitable spot in the uterus before beginning to attach. During the adhesion process, the molecules on the outside of the embryo interact with the uterine lining so that the embryo sticks on the uterine wall. In the last step of the implantation process, the embryo will begin to form a blood supply connecting to the uterus, which gives the embryo a source of energy and allows the placenta to grow.
The exact days that each of these steps happen can vary. For instance, a day 7 embryo may have already “hatched” before transfer, and some embryos develop and implant slightly faster or slower than others.
Once the embryo has completed implantation, the placenta can begin growing, and the placenta will support the pregnancy throughout the next several months.
Days 7-14
The exact days may vary, but after implantation until around day 14, the embryo will undergo the following changes:
- Cells that will become the placenta multiply and grow deeper into the uterine lining.
- The yolk sac is formed.
- Cells flatten into a bilaminar embryonic disc.
- The primitive streak can appear, which is an indentation in the embryo that the fetus will form around.
While a pregnancy may be detectable around day 9 or 10, most fertility clinics want to wait 14 days (hence the two week wait). After 14 days, you or your surrogate will return to your clinic for a pregnancy blood test.
What happens to a day 7 embryo in Surrogacy?
Embryo transfer usually happens sometime between day 3 and day 7 of embryo development, depending on your fertility specialists’ assessment and recommendations. That means that in most cases, by day 7 your embryo will be in your gestational carrier’s uterus, and implantation and pregnancy may follow shortly.
The process after the transfer will look similar to IVF without a surrogate, but it will be happening to your surrogate. When you are going through a surrogacy journey, you can communicate with your surrogate about what she’s experiencing throughout the two-week wait. After the two weeks, she will undergo a pregnancy blood test to test her hCG levels. If you’d like to be present for this big milestone, you can make the appropriate arrangements.