Ready for some fun science?
Hold on to your chair, because this is where shit gets interesting.
Yesterday they collected the eggs from the follicles, and they fertilize them on the spot. But not by just letting them take a bath in a pool full of swimmers — nooooooooooo — that would be way to easy.
What they do for mine is ICSI – Intra-cytoplasmic sperm injection. They take a single swimmer, chop its tail off so they can aspirate it into a needle, then inject it directly into the egg. (About 75% off eggs survive this procedure.) Of the 29 eggs retrieved yesterday, 21 were mature, which is more than the 17 we had counted on the ultrasound a few days earlier. (Hooray, 4 more!)
From a pool of 85 million, the embryologist selects one swimmer for each egg.
How do they select which ones make the cut? I heard that they place the sample on a gradient, and pick from the strongest uphill swimmers. But Google reveals that they expose the sperm to Hyaluronan (not sure what that is), and those that bind well to Hyaluronan tend to have a better fertilization rate, as it is a marker for a better set of chromosomes. That’s all I can tell you on this topic, given that I just learned this. I like the gradient version of the story better, but oh well.
Why not just let the egg bathe in swimmers? You can actually do it that way, and many women do – particularly those who are younger and tend to have better chromosome counts. At 41, only 30% of my eggs have normal chromosome counts, so we want to be able to perform CCS – Comprehensive Chromosomal Screening – on them to ensure that we only put back in embryos that have a normal chromosome count. If you throw a bunch of sperm at an egg, and one sperm fertilizes, the chromosomes from the sperm that didn’t make it inside the egg will remain on the outside of the egg. At day 6, when cells from the embryo are biopsied, these chromosomes from non-successful sperm will contaminate the results. That’s why if you are doing CCS, you have to do ICSI. One egg, one sperm, and on Day 6, screen the chromosome count.
It is the end of day 1, and we just heard that we have 16 successfully fertilized eggs remaining. This too is a great start. From here, the odds are that 50% will make it to day 6 (so, down to 8) and then 30% will be genetically viable, (so, 2.4).
If we end up with 2 or 3 viable embryos, that would also be a great start. If you implant (aka: “transfer”) a viable embryo back inside, there is a 60% chance it will result in a healthy full-term live birth. Having 1 viable embryo is good, but having 2 or even 3 really raises the odds of success.
It is far too early to get my hopes up, having had them dashed last time, but last time on day 1 we were already down to 3.
There is still a long road to travel, but 16 is about as good as one could hope for. You can let go of your chair now.