What percentage of fertilized eggs make it to day 3?

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1 fertility expert(s) answered this question

Answer from: Raúl Olivares, MD

Gynaecologist, Medical Director & Owner Barcelona IVF
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In normal circumstances, 90% of the embryos that we get on day-1 should reach day-3, and if they don’t, it tends to be because there is probably an egg factor.  As a general rule, though it’s something that should be discussed in each case, we consider that the embryo in the first 3 days leaves from what it gets from the egg. The DNA of the sperm is activated on day 3. If you have embryos with problems during the first three days of development, it’s mostly due to the egg quality. If the embryos reach day 3, and they suddenly get worse,  this is something that can’t be due to a problem related to the sperm or the male DNA. Of course, that means that if you are  42-43,  you may start having very poor quality embryos from day 2, but if you are dealing with a male factor or with a tubal factor, and you are young, I would say that between 90 or even 100% of the embryos with different qualities should make it to day 3.

The main problem and the most critical day for the embryos is day 4 to day 5. That’s why considering to transfer on day  3, should never be done. You may be transferring embryos that look great on day 3, but they are not going to become a blastocyst. I’ve seen in some cases, patients who have been asked for different implantation tests and have never had a single blastocyst. They have always had transfers before.  In these cases, likely the main problem is that those embryos didn’t become a blastocyst, and then it would have been unnecessary to carry out any implantation issues.

Whenever you can, take the embryos to day 5,  even if they don’t make it to day 5, it’s going to be really useful. I prefer not to transfer the embryos without knowing the real quality. If I only have 1 embryo and I take it to the blastocyst stage, and it does not become a blastocyst, there’s going to be bad news anyway for the patient, but at least, we are going to be sure that the problem is in the embryos, and we are not going to waste time and money asking for implantation tests that are not needed at all.

About this question:

What is the average number of oocytes becoming a day 3 embryos?

Day 3 embryos are called “cleavage” stage” embryos, we are looking for at least 8 cell embryos. What number of oocytes will become a day 3 embryo? Do all embryos make it to Day 3?

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