3DT vs. 5DT

One of my readers asked me to do a post on day three transfers versus day five transfers, and I'm more than happy to oblige. I've talked a bit about my own struggle to understand this topic and make a decision on when to transfer before.

My basic understanding of the difference between a 3DT and a 5DT is this: 3DT's are usually used when there are fewer embryos to choose from and their development is clear cut (i.e. variations in grades and quality). 5DT's are used when there are either many embryos that have fertilized or where there are several embryos all about the same grade and quality on day 3.

My embryologist told me last cycle that the battle for an embryo to become a blastocyst (or the transition from day 3 to day 5) is the hardest journey that the cells make. Between day 3 and 5 the embryo has to become it's own life form and survive as its own self-sufficient organism. She described the transition from day 3 to day 5 as a cellular civil war. On average, only about 30% of embryos make it to the blastocyst stage; that means more than half of your fertilized embies will arrest by day 5. Scary, right?

The popular debate between day 3 transfers and day 5 transfers is the argument that perhaps an embryo would have survived if it was transferred earlier. Some RE's prefer day three transfers because they believe an embryo has a better chance of survival in utero than in a lab.

I don't necessarily believe this and here's why - in a normal pregnancy (non-ART conception) the embryo would not be released into the uterus (which is where an embryo is placed at transfer) by the fallopian tubes until day 5. So really, in my opinion, there's no difference between the uterus and the lab, per se. And a lab could probably mimic the conditions of the fallopian tubes better than a uterus could.

This interesting article that I found goes so far to say delayed transfers (i.e. day 5 or 6) deliver "embryos to the uterus at the time they would normally arrive, avoiding exposure to potentially harmful amino acids and carbohydrates."

Also, by waiting till day 5 you have an embryological version of Darwinism (you know, survival of the fittest?). By extending your transfer out to day 5, it becomes clear which embryos (or at that time blastocysts) are the strongest and most resilient, making an obvious case for transfer.

My dear friend Linsday shared this article with me regarding the reasoning behind day three (over day 5 transfers), and I found the content to be really eye opening. Here's a little snippet:

There are numerous reasons for continuing to perform day three transfers: its cheaper, its less work for the lab, lower liability because the lab has the embryos for a shorter period of time, everybody makes it to transfer, if the cycle doesn't result in a pregnancy, the program can still look good, etc. You'll notice I didn't say anything about a day 3 transfer improving your chances of getting pregnant - it doesn't. The reason programs continue to transfer day 3 embryos is because its more convenient for the lab and the docs. …

The rationale for a day 3 transfer is to get out from under the "blame" for the failing embryos. By transferring failing embryos on day 3, the program also transfers the responsibility for the subsequent failed cycle to the patient. It is a subtle manipulation of the patient's emotions. Here's the scenario: "We're so sorry the cycle didn't work, but you know the embryos were still growing when we transferred them. We don't know what you did to them afterwards. Wanna try again?" Using this pyschological manipulation, it becomes the patient's fault the cycle didn't work, not the program's. See how it works?

Crazy and interesting, right? Now clearly this is just one doctor's opinion and there are many others out there, but this one struck a chord with me, well, cause it just made sense.

With IVF #2 we had 12 eggs fertilize. On day three they were all doing stellar, and we were pushed out to day 5 so that the embryos could weed themselves out. For personal reasons regarding the disposal of one of our blast stage embryos during IVF #1, we had requested to do a day 5 transfer regardless of the number of embryos we had.

Now, having said all of this, I should also say that with IVF #1 (only 5 fertilized embryos that cycle) we did a 3DT and got knocked up. Was that because the embryo had a better chance of survival inside me? Because the embryologist had observed our embryos long enough to knowingly select one of the strongest for transfer? Or was it just luck of the draw?

Truly, I have no idea. People get pregnant all the time from 3DTs and from 5DTs. For me, personally, as a multiple IVFer, I'm just more comfortable with things at the day 5 stage for all of the reasons I've just shared. Best of luck in your cycle!