# Blastocyst questions



## clucky

Hi Crystal -its so good of you to do this board 

I wonder if you can explain how the stats for Blastocysts work? I am confused by my google research!
If the average pregnancy rate from a day 3 transfer is, say, 35%, and from a blastocyst transfer is, say, 50%, but only 50% of day 3 embies make it to blastocyst in the lab, does this mean that there are some embies which could form a viable pregnancy from a day 3 transfer but would not otherwise survive? So for a 'batch' of embies would we get the best outcome if we always went for day 3 transfer and froze any good day 3 embies for future FET?

Also, we have always had really good day 3 embies to transfer, but on our last cycle we went to blastocyst. We had seven 8-9 cell embies on day 3 but by day 5 we just had 2 blasts - one grade BB, one BC. Does that indicate a problem with our embryo quality?

thanks so much for your help 
Clucky xx


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## CrystalW

clucky said:


> Hi Crystal -its so good of you to do this board
> 
> I wonder if you can explain how the stats for Blastocysts work? I am confused by my google research!
> If the average pregnancy rate from a day 3 transfer is, say, 35%, and from a blastocyst transfer is, say, 50%, but only 50% of day 3 embies make it to blastocyst in the lab, does this mean that there are some embies which could form a viable pregnancy from a day 3 transfer but would not otherwise survive? So for a 'batch' of embies would we get the best outcome if we always went for day 3 transfer and froze any good day 3 embies for future FET?
> 
> Also, we have always had really good day 3 embies to transfer, but on our last cycle we went to blastocyst. We had seven 8-9 cell embies on day 3 but by day 5 we just had 2 blasts - one grade BB, one BC. Does that indicate a problem with our embryo quality?
> 
> thanks so much for your help
> Clucky xx


Hello clucky,

I think 50% of embryos making it to blastocyst is quite elevated - i think your result of 2 blasts from seven embryos is much more what i would expect. BB and BC are nice quality blastocysts and i have seen many pregnancies from this grade of blastocyst.

Choosing whether to do Day 3 or blastocyst is always a balancing act - generally we believe the womb is the best place for embryos but we need to keep them out long enough to choose the best ones from a group. Blastocyst culture does help us be a lot more certain about choosing the strongest when there is a group of similar embryos.

The drawback of having a day three ET and freezing is that if there is a group of similar embryos it may be that the best one is frozen rather than going back fresh and the freezing process can compromise that best embyro.

A lot of studies and statistics support doing blast transfer rather than day three and freezing but you should ask your clinic for their relative statistics per *egg collection * of day three plus freezing vs blast.

Best wishes


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## clucky

Just wanted to say Thanks Crystal - that's really helpful!
clucky x


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