My snow babies

Okay, that one’s not mine.  When I read various infertility blogs, the ladies (it’s always ladies, right?) would refer to their frozen embryos as snow babies, frosties, snow flakes, etc.  So, about my snow babies….

After my last IVF attempt, we froze three day six blastocysts (none of them reached blastocyst at day five):

·       Day 3: 8 cell => Day 5: morula level 2, late cavitation => Day 6: blastocyst level 3, hatching

·       Day 3: 6 cell => Day 5: morula level 2, late cavitation => Day 6: blastocyst level 3

·       Day 3: 7 cell => Day 5: morula level 2, late cavitation => Day 6: early blastocyst level 3

It’s better for the embryos to reach blastocyst by day 5, and there is evidence that fresh day 5 blastocysts are significantly more likely to be successful than day 6.  (http://www.ncbi.nlm.nih.gov/pubmed/11384637)  But my lab says their pregnancy rates are the same with frozen day 5 blastocysts and frozen day 6 blastocysts.  (That is also supported by some medical literature: http://onlinelibrary.wiley.com/doi/10.1111/j.1471-0528.2011.03101.x/pdf)  So the fact that my guys did not make it until day 6 is not a further strike against them.

After my miscarriage, I discussed my frozen embys with one of the doctors at the office, lamenting that the “good one” didn’t take, so what was the chance one of the “crappy ones” would.  She looked at my chart and said that the hatching B3 had numbers that were basically the same as the B2 we ended up using, and that rating is not an exact science, and that she thought the chances could be similar to the B2.  She did look at the poor little early blastocyst level 3 and say, “I doubt they’d pick that one.”  Poor crappy early B3.

Interestingly, it is the LAB, and not the doctors, who pick the embryos to thaw.  The embryologist picks the one it thinks looks the best, starts thawing one embryo at a time until it finds one that looks good, and that’s the one used.  (If someone is using more than one emby for transfer, the lab will keep thawing until they have two good ones.)  The expected survival rate after thawing is about 85% at my lab.  (It used to be only 50%.)

On our transfer day, the lab chose the day 5 six cell B3.  (I.e. not the hatching one or the early “crappy” one.)  I asked a lot of questions about why that one was selected over any of the other ones, and was told that once they are frozen as B3s, they’re all kindof treated the same, and their background is less important.  But that particularly B3 had developed nice enough, so they thawed it, it survived, and bombs away. 

It’s still not clear to me why the “hatching” one was not selected.  One doctor I talked to seemed to think that was the best one, and I’ve read articles that suggest hatching blastocysts have better success rates: 

Hatching Day 6 
(Yoon HJ, Yoon SH, Son WY, Im KS, Lim JH., High implantation and pregnancy rates with transfer of human hatching day 6 blastocysts, Fertil Steril. 2001 Apr;75(4):832-3.)

My doctor did say for all of their frozen embryos, they do assisted hatching, so maybe that’s why.

They showed me a picture of my day 5 six cell B3.  It reminded me of a butterfly with injured/wet wings.  The doctor assured me that it would continue to unfold and look even better by the time it was implanted.  After an embryo is thawed, it is no longer possible to accurately rate it.  (Not that the ratings are so accurate when they are fresh.)  They can tell if it looks viable, but they can no longer say if, after the freeze, it’s a B1/B2/B3. 

Lucky for us, the first one the lab picked thawed, so “hatching” and “crappy” are still on ice.

P.S. In the Urban Dictionary, a “snow baby” is defined as a “a child born to a mother/father who was abusing either heroin or [cocaine]/crack/freebase at the time of [its] development in the womb/birth.”  Don’t look up how the Urban Dictionary defines “frostie.”  I’m scared to search the definition of “snow flake.”  Hmm.  Maybe we have to come up with another euphemism for our frozen embryos, ladies.