FET single embryo
6 Replies
cristina_nyc - November 28

Many thanks for your thoughtful answers on this forum. I've learned so much just from reading old posts. Infertility is such a difficult journey, and resources like this are incredibly helpful.

I'm 31 and have PCOS. IVF#2 resulted in a twin pregnancy, which I lost at 17 weeks due to incompetent cervix.

I have 6 frozen day 5 blastocysts from that cycle:
- 1 completely hatched blast, grade 1
- 1 hatching blast, grade 1/2
- 4 hatching blasts, grade 2

Also, when I had my fresh transfer on day 4, I had one grade 1 embryo and one grade 2 embryo (which were transfered). All the other embryos were poorer quality (not sure of specific grades) on day 4. Does that have any bearing on the quality of these frozen blasts? Or, now that they made it to blast, their status on day 4 is irrelevant?

Given my poor outcome with twins, I do not want to have another twin pregnancy. However, I know that success rates with FET are lower in general, and I worry about lowering my chances even further by doing a single embryo transfer.

Given my embryo grades, what do you think are my chances of success with a single embryo transfer? what would be success rates with 2? What are chances of twins if I decide to transfer 2?



Dr Smith - November 29

All blastocysts are not created equal. There are different grades for blastocysts that relate to their developmental potential. Most programs will not freeze blastocysts of poor developmental potential to spare the patient the disapointment of poor post-thaw survival. Assuming that you program for these guidelines (freezing only Gade 1 and 2 blastocysts), we can assume they were of adequate developmental potential to justify freezing. So, to answer your question, if they developed into "good" quality blastocysts by Day 5, their grade on Day 4 was not very important.

Your second question is a bit tricky and would depend a great deal on the FET success of your program. If you live in the US, your program's most recent FET success rates are published and are available from The Society for Reproductive Technology on their website (http://www.sart.org/find_frm.html#). Ask your doctor how many embryos they routinely transfer for an FET and this will give you some idea of what your chances would be with 1, 2, or 3.


cristina_nyc - December 9

I transferred 1 hatching blastocyst, grade 5BB. It was originally frozen on day 6.

I had 2 5BB's, but was only going to transfer 1, so the embryologist selected the one that had made the most progress out of it's shell. He said it had progressed a bit in the couple of hours since thawing.

What do you think are my odds of success with a FET of a 5BB blastocyst?



Dr Smith - December 11

It is impossible to predict your particular chance of success because programs vary in their FET success rates. There are many factors involved other than the developmental potential of the embryo. For example, the skill of the physician performing the transfer, the receptivity of your endometrium, etc. I'm sorry, but you will have to wait it out.


cristina_nyc - December 11

Thanks for your response. Believe me, after all I've endured with IF, I know that there are no guarantees. Even under the most favorable circumstances, luck plays a bigger role than we would like it to.

I guess my question really is this -- Does a 5BB day 6 frozen/thawed blast likely have what it takes to make a baby? Or is it sub-optimal?



Dr Smith - December 13

It is slightly "sub-optimal" (as reflected in the "BB" grade), but I've seen many pregnancies following the transfer of "BB" grade embryos. However, these were fresh transfers. TRansferring a single frozen-thawed 5BB is less likely. Don't want to be Dr Doom 'n' Gloom here, but I think your chances aren't so great. There, you pulled a prediction out me and I try so hard not to look in my crystal ball... Best of luck and you're right luck plays a pretty big part in all of this. Science/Medicine can only take us so far.


cristina_nyc - December 13

Thank you for your honesty. That is what I wanted. I don't need "baby dust" or any of that nonsense, I just want to know the scientific odds.

I knew going into this that my best chance would be to do another fresh cycle (esp since I'm doing single embyo transfers from now on), but figured I might as well use up what I had in the freezer.

Thanks again,



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