This is a perpetual Google topic of mine. Is there a difference between Day 3 and Day 5 transfers and is there an advantage in one over the other? Is a Day 5 blastocyst transfer better than a Day 3 cleavage stage transfer? What about Day 5 versus Day 6 embryos? Is a Day 5 blastocyst better than a Day 6 blastocyst?
Day 5 blastocyst transfer success rates are potentially confusing because almost all clinics that do extended culture, transfer only blastocysts and don't do any transfers on Day 3, they don't have anything to compare it to. I think many of them do this because for many clinics, it will seem more sensible, than transferring 2 cells on Day 3.
However, this does not necessarily mean that having a blastocyst transfer increases a couple's chance for pregnancy. It means that if we select patients for blastocyst transfer that are often younger and have more embryos that look better under the microscope (better embryo "quality") — we should have higher success rates — because we already know that those patients are more likely to have success — regardless of whether we transfer their embryos on day 3 or 5.
This is true, as most clinics report a 60–75% success with transferred blastocysts, as opposed to slightly lower with transfer of late-stage embryos, or day 3 embryos.
These are the source links quoted in the post, in order:
fertilityfile.com/2011/01/23/embryo...
www.fertility.ca/2009/07/ivf-choosi...
fertilegrounds.dominionfertility.co...
www.advancedfertility.com/blastocy...
www.sfgate.com/news/article/Human-e...
www.drmalpani.com/embryologist_faqs...
www.ivf.com/blastocyst.html
www.advancedfertility.com/blastocys...
www.advancedfertility.com/implantat...
m.humrep.oxfordjournals.org/content...
onlinelibrary.wiley.com/doi/10.1002...
www.fertstert.org/article/S0015-0282(08)00740-1/abstract
haveababy.com/fertility-information...
However, this does not necessarily mean that having a blastocyst transfer increases a couple's chance for pregnancy. It means that if we select patients for blastocyst transfer that are often younger and have more embryos that look better under the microscope (better embryo "quality") — we should have higher success rates — because we already know that those patients are more likely to have success — regardless of whether we transfer their embryos on day 3 or 5.
