I continue to worry about damage to a potentially viable blastocyst during the freeze/thaw process. At very high quality labs, about 90% of frozen blastys will survive the thaw. (See article below, which shows just a hair under that.) But what about that last 10%?
A doctor at my office suggested that high quality embryos survive the thaw at a higher rate than poor quality ones, so maybe the freezing process is just another method of weeding out embryos that are unlikely to work. (My lab has about an 85% survival rate, but he suggested it might be as high as 90% with good quality embryos, which means there is still some loss of potentially viable embryos.)
At high quality labs, the implantation rate using frozen is the same as fresh. Blastys have to be of a higher quality to be frozen than to be transferred fresh, so that’s not a surprise. While the implantation rate is similar between fresh and frozen, my lab suggests that frozen have a higher miscarriage rate.
At the end of the day, there is no question that freezing causes some damage to cells in the freezing process. The only question is whether it is catastrophic.
Like anything, there are good things about freezing and bad things about freezing. We know the bad, but what about the good? Among other things, I’ve read that the stim process is hard on your body and, theoretically, you should be able to grow a better lining if you have a chance to do that without a harsh stim cycle right on top of it. Here’s a non-medical journal article that suggests frozen cycles result in better outcomes for babies than fresh cycles:
Of course in our case, we still decided to transfer a fresh one because we were not sure we would have more than one embryo (we were wrong) and we did not want to risk anything in the freeze/thaw process.
And, no surprise, the better a fresh embryo looks, the better it’s likely to look when it’s thawed. This article goes through prediction of success in a frozen cycle based on pre- and post-freeze ratings:
Don’t skip the tables—they’re the most interesting part! Unsurprisingly, the best quality fresh blastys make the best quality thawed blastys. Better blastys resulted in better outcomes. Faster expanding frozen blastys are better (double the pregnancy rate!). Having a failed cycle (or more) did not appear to have a significant impact on success. As we’ve already discussed, doing a freeze of a blasty that hits at day 5 versus day 6 made no difference on outcome. Unsurprisingly, there is much greater success for women under 37. It also notes that their clients that used ICSI had more success. (I’ve read elsewhere that is not necessarily true.) Also interestingly, people with MORE than 16 follicles or more than 11 eggs had LOWER outcomes. (More is not better!) Everyone knows that being “overweight” is not good for fertility. But this article says BMI of less than 22.8 is best. (I calculated mine—I’m in the 21s. I do not consider myself to be overweight at all, but I’m around five pounds away from the bad BMI. A BMI of 22.8 isn’t even considered overweight!!) So forget being “not fat”—you have to be downright skinny.
Here’s another interesting article on freezing:
Anyway, it seems like there is some risk to the freezing process, but that for most people it may be worth the risk.
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