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A big decision that comes along with IVF is whether to do a day 3 vs. day 5 embryo transfer (ET).
Many studies seem to agree that day 5 embryo transfers have a higher success rate. Yet that doesn’t mean day 5 transfers are the best option in all cases. Genetic testing, fertility lab capabilities, and risk of multiples are a few other factors that should be considered.
Keep reading, and you’ll get a full look at the pros and cons of day 3 and day 5 ETs.
What’s a day 3 embryo?
A day 3 embryo refers to an embryo that’s spent three days growing in a lab under the careful watch of an embryologist. Sometimes day 3 embryos are also called cleavage stage embryos.
One important thing to know about 3-day-old embryos is that they only have between 6 to 8 cells.
What’s a day 5 embryo?
Similarly, a day 5 embryo has spent five (possibly even 6 or 7) days developing in the laboratory. At 5 days old, the embryo is considered to be in its blastocyst stage.
Even though it’s only about 2 days older, a day 5 embryo may have more than 80 to 100 cells. With all those additional cells, day 5 embryos are more developed and structurally organized.
At this stage, those tiny cells form both the inner cell mass and the trophectoderm. These are the structures that mature into the growing fetus and placenta.
Clearly, day 3 embryos and day 5 embryos are quite different. So let’s see how this impacts the embryo transfer process.
Day 3 vs. day 5 embryo transfer: At a glance
There are several key embryo transfer factors you should know about. These include success rates, genetic testing, risk of multiples, and fertility lab quality.
Take a look at the image below to see how each of these measures up for a day 3 ET vs. day 5 ET.
At first glance, there seems to be more upside to using day 5 embryos. For one, an embryo at day 5 has a smaller risk of being chromosomally abnormal.
Think of it as a survival of the fittest scenario (because that’s essentially what it is). Those two (or more) extra days of development help weed out unfit embryos. The embryos that don’t make it likely weren’t healthy enough to make it to a live birth. So basically, this self-selection process can reduce your chances of having a miscarriage later on.
Don’t get the wrong impression here though. None of this means that there’s anything wrong with doing a day 3 transfer. In fact, later on, we’ll talk about when a day 3 transfer could be more beneficial.
But first, let’s more carefully examine what the latest research says on the differences in success rates.
Day 3 vs. day 5 embryo transfer success rates
Here’s a look at what current research suggests about day 3 embryo transfer and day 5 blastocyst transfer success rates.
In sum, the research seems to show that success rates are more favorable with Day 5 transfers and sequential transfers.
All this data is helpful to keep in mind when making your decision. But don’t forget, success rate isn’t the only factor to account for. Keep reading to learn about the role that genetic testing plays in embryo transfers.
Genetic testing for day 3 and day 5 embryos
Let’s say you’re planning on doing genetic testing for your embryos. In that case, it may be in your best interest to go with day 5 embryos. Let’s explore why!
Preimplantation genetic testing requires an embryo biopsy. This is when 1 to 2 cells are taken from the embryo so that they can be more closely inspected.
But there is a difference in doing a biopsy on a developing embryo on day 3 vs. day 5. In fact, studies show that doing genetic testing on day 3 embryos can decrease the chances of successful implantation.
Why is this the case? Think back to when we talked about the structure of a day 3 embryo vs. a day 5 embryo. 3-day-old embryos only have about 6 to 8 cells. 5-day-old embryos, on the other hand, have more than ten times that amount.
When the cells are taken from a day 3 embryo for biopsy, there’s a heightened risk of damaging the forming blastocyst. But when a biopsy is done on a day 5 embryo, there’s much less risk. This is mainly because the blastocyst has already formed.
Speaking of risk, let’s also discuss how the risk of multiple births compares for day 3 vs. day 5 embryos.
What’s the rate of multiples for day 3 and day 5 embryos?
In general, there’s a higher rate of conceiving twins or multiples with a day 3 ET. But let’s better understand the science behind this phenomenon.
One study found that opting for a day 5 ET (aka blastocyst transfer) is a good way to reduce the amount of embryos needed. It also decreased the rate of multiple gestations and increased pregnancy rates.
Another study found that the single blastocyst transfer (SBT) group had much higher rates of implantation. And the day 3 double embryo transfer (DET) group had more incidences of multiples.
What’s the bottom line here? If you’re doing a day 5 transfer, you’ll likely do a single transfer. This is because there’s a higher chance of pregnancy with a day 5 embryo.
If you’re planning on doing your ET on day 3, you may transfer more than one embryo. This is because the implantation rate for day 3 is lower, and you may wish to boost your chances with more than one embryo.
At this point, you’ve seen success rate, genetic testing, and rate of multiples for day 3 vs. day 5 ETs. Let’s move on to consider one more factor: the quality of your lab.
How does lab quality factor into a day 3 vs. day 5 ET?
Growing your embryo to the blastocyst stage requires a high-quality environment. This optimal environment includes the just-right temperature, humidity, oxygen tension, and nourishment.
As you can imagine, achieving these conditions requires a lot of resources. That’s why it’s important to consider the quality of the fertility clinic you’re using.
Some laboratories may not have the ability to grow your embryo to day 5. And in this case, you may need to opt for a day 3 ET. If that’s the case, don’t feel bad. There’s nothing wrong with doing a day 3 embryo transfer. It will still boost your chances of getting pregnant!
Maybe you’re still skeptical and wondering: Does it really matter that much if you do a day 3 or day 5 transfer?
So let’s do a final overview of which option could be best for you.
Day 3 or day 5 embryo transfer: Which should you choose?
In short, there’s no one right answer here. The right timing is completely dependent on your situation and fertility goals.
Yes, the research does show that embryos are more mature and chromosomally sound at day 5. And this usually translates into a higher chance of getting pregnant.
But in certain cases, there could be benefits to choosing a day 3 ET over a day 5 ET. For example, women who have fewer healthy eggs could risk losing the embryos altogether if they wait past day 3.
This is because the embryos may have a better chance of survival once they’re transferred to the uterus. And when they are left to keep growing in the lab those extra two days, they may die off before even having a chance at transfer.
Nevertheless, let’s look at the table below to see which route may be the best match for your situation.
Of course, your unique circumstances may not fit into any of these scenarios. So be sure to consult with your doctor or fertility specialist. They’ll be able to help determine the best course of action for your transfer.
One last question that may be on your mind as you contemplate this decision is how the transfer timeline affects your due date. So we’ll break this down in the next section.
How can I calculate my estimated due date (EDD) based on the embryo transfer day?
First, let’s see how a woman’s EDD is calculated when no assisted reproductive technology (ART) is used.
In the chart above, the day of conception can be determined by accurately tracking your ovulation day. Using a fertility monitor like the Inito monitor can help with confirming ovulation.
But in some cases, you may not know precisely when you ovulate. And that’s why you may need to use the date of your last menstrual cycle.
Now, let’s see how you would calculate your EDD in an IVF cycle.
In case you’re curious, here’s a little more on how we got to these calculations. In an IVF cycle, the embryo transfer day is considered to be the first day of the pregnancy. This would be equivalent to the conception day (or ovulation day) in a non-ART cycle.
Takeaways
- Doing a day 3 vs. day 5 embryo transfer is a big decision. The right option for you depends on your unique circumstances and goals.
- Day 5 embryo transfers tend to have a higher success rate based on the latest research.
- Studies have shown that day 3 embryo transfers are associated with a greater chance of multiple births.
- Not all fertility labs are equipped to manage embryos past day 3. So this could impact your transfer options.
- If you want genetic testing done, it’s better to go with a day 5 ET since there’s a lower risk of implantation failure.
- For women who have a diminished ovarian reserve, a day 3 ET may be a more suitable option.
- To calculate your EDD with a day 3 transfer, add 263 days to the date of your transfer. For a day 5 transfer, add 261 days to the date of your transfer.
- Talk to your doctor to decide on a transfer timeline that best meets your needs.
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- Effect of Day 3 and Day 5/6 Embryo Quality on the Reproductive Outcomes in the Single Vitrified Embryo Transfer Cycles
- Comparison between sequential transfer vs. day 3 and day 5 frozen embryo transfer in IVF patients
- Day-3 vs. Day-5 fresh embryo transfer
- Comparing the effect of sequential embryo transfer versus double blastocyst embryo transfer on pregnancy outcomes in intracytoplasmic sperm injection (ICSI) cycles in patients with repeated implantation failure: A randomized controlled trial – ScienceDirect
- The number of biopsied trophectoderm cells may affect pregnancy outcomes – PMC
- Blastocyst transfer: A useful tool for reduction of high-order multiple gestations in a human assisted reproduction program – ScienceDirect
- A retrospective comparative study of double cleavage-stage embryo transfer versus single blastocyst in frozen-thawed cycles | Middle East Fertility Society Journal
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