I've gotten pg on both. I agree with Spencer, it depends on how many you have and how they look. Just because an embryo makes it to blast doesn't mean it has any type of guarantee on implanting. I've seen 3 day embryos turn into twins and 5 day. There doesn't seem to be any ryhme or reason to it. My last DE, I did blast, one implanted and then I m/c. 3 day seems to be my ticket at this point with the last BFP.
i'm sorry this is not more definative.
IVF 1# ICSI & AH-BFN 04/08.
After too many failed natural cycles to mention, discover that previously clear tubes have become blocked after surgery to remove fibroids (however, no more fibroids). Decent FSH for 40 year old
My understanding is that it depends on how many embies you have and how they're developing.
If you have fewer embies (e.g. I had 2 b/c it was a frozen oocyte cycle) then they often go for a day 3 transfer b/c
This is my opinion and by no means should influence your decision but I did my first transfer this past December and they did a 3 day transfer even though this donor has been 5 day for the other recipients. My results are an ectopic pregnancy which I am still dealing with. My first methotrexate shots were administered out of town because we were on vacation when we found out we needed the shots. We asked the other doctor at this other clinic why this ectopic occurred and he said they have rare ectopics but have noticed they seem to occur with the 3 day transfer because the embryos aren't as mature and tend to float when placed in the uterus because they still have days of development before implantation while the 5 days implant within 24 hours so there is less chance of moving around.
I also like knowing that the stronger embryos are being implanted so if there are issues you will know before getting that BFP and then having it disappear because it didn't develop properly.
this is just my opinion but I hope it gives you something to think about and ask your RE.
TTC #1 since 2005IUI #1 - chem. pregnancy, IUI #2 - BFN 5/2007 -BFP naturally, m/c 6/07 IUI #3 - BFN, IVF#1 canceled-IUI #4 & IUI #5 -BFNET 12/4 - Ectopic. Waiting for levels to go down.