If the embryos are already frozen on day 3, they can be thawed, biopsied, and get results back in time to transfer by day 5. If fresh, same applies - they can biopsy day 3, get results by day 5 for transfer. Not every embryo will give a result though w/ the testing on day 3 (we did 10 embryos I think, and several came back with "no signal" so we couldn't tell.
If you biopsy on day 5, the results are more certain (you should get a result on every embryo tested) but you won't be able to transfer on the fresh cycle. If you thaw frozen blasts and biopsy you'd then refreeze, and thaw and transfer when you get results. I don't like the double-freeze, but it's definitely an option. W got pg doing this with her frozen blasts; she transferred two and got twins.
I highly recommend PGS (the newer version - tests all 23 chromosome pairs vs. just a few with PGD). We did it on a fresh cycle on day 3 and had a day 5 transfer, as we wanted to transfer only one blast - it worked
. I really enjoyed this pg so much more, too, knowing that the baby was ok chromosomally. (Had a ton of early bleeding and complications but knew the baby was normal, so didn't have to worry as much about the cause of all that.)
One caveat - you only want to do this at a clinic that does it regularly - the experience of the embryologist is key, as the embryos can be damaged in the process (ours weren't, at least by appearance, all made it to freeze 2-3 days after biopsy and still looked good).
Good luck to you! Best wishes for success soon,
Kenny