More and more IVF clinics are inclined to implant developing eggs at the day 5 over day 3. What are the reasons? And what is the basis on which one to chose?
Pro:
On a most basic level 25% of 3 day embryos are normal vs. 65% of 5 day, which are now a blastocytes, are normal. Most clinics want to have the highest success rates possible. People chose to come to a clinic based on its success rates. So there is a survival mechanism to one element. That is one of the reasons they have an age limitation to whom they will work with. At some point it is against the odds that you will conceive.
The 5 day is at the stage where it is ready to implant, where as the 3 day has a couple of days of waiting around and developing before it is ready to implant.
By day five the women has much more progesterone in her body, which aids in implantation and maintaining implantation.
Con:
A key element is the embryo is utilizing the genetic “gas” of the mother’s mitochondria. At the point of day 5 it must transfer to making and using it’s own gas to developed further. But the increase exposure to oxygen creates more “oxidative stress” which damages DNA. The natural embryo or blastocyte gets minimal exposure in utero. Does this increased exposure and damage of the 5 day reduce the effectiveness of the blastocyte’s own genetic DNA?
Recently it has been discovered that there are small groupings of cells in the uterus called pinopods that look like a cluster of mushrooms and act like a landing pad for the blastocyte. Is it possible that the developing embryo releases some kind of chemical that aids in the initializing of these pinopods and prepares them for receiving the blastocyte?
Currently there are no real concrete answers to the above questions, but they are a beginning place to begin thinking about the issues should you be preparing for an IVF and having to confront day 3 versus day 5.
