I called Terra early in the morning and had her get Miles on the other line, preparing them for the good news about their embryos. To review, we retreived 15 eggs. Out of those, 11 were mature. Out of those, all 11 successfully fertilized. Today this is what we had:
(10cA) (9cA) (9cA) (8cA) (8cA) (8cAB) (6cB) (8cB) (8cB) (degenerate) (degenerate)
Just as different schools have different grading systems ( A / B+ / C- / F vs 100% / 95% / 45% vs High-Honor / Honor / Pass / Fail ) so different embryology labs have different scoring systems. The embryo grading system we use in this particular lab (for Day 3 embryos) is as follows. The # refers to how many cells are present. The letter is a grade representing how fragmented the embryos is. A is excellent, meaning there is no fragmentation. AB is like A-, meaning it’s not quite as fragmented as a B, but is also not as perfect as an A.
The reason we grade embryos is to help us estimate the odds of getting a baby from them. If we have High-Chance embryos, then we wouldn’t want to put in as many, for worry about twins or triplets. If we have Low-Chance embryos, then we can safely put more in. In fact, with Low-Chance embryos, we SHOULD put more in so as to have a higher of success. I coined the simple terms Low-Chance and High-Chance and use this terminology the way other people use the terms Low-Quality Embryo and High-Quality Embryo. I prefer this terminology to avoid the incorrect perception that a baby that comes from a Low-Quality embryo is someone less healthy than one from a High-Quality embryo.
The three factors that determine if a day 3 embryo is High-Chance vs Low-Chance are as follows:|
- CELL NUMBER: When a sperm fertilizes an egg, a 1-cell embryo is created. The cells then begin to individually divide. One cell splits into two. Then each of the two new ones will split into two more each. Because the splitting does not all happen exactly at the same time, we aren’t restricted to seeing 1/2/4/8/16 cell embryos. That’s why you can sometimes have a 7-cell. In that case, you have a 4-cell embryo and 3 of them split, while the 4th has yet to split. In general, embryos that are 6 cells or greater by day 3 have a much higher chance of becoming a baby than embryos which are less than 5 cells. There are some more subtle factors to consider, such as time-of-day (a 5-cell early in morning might be a 7-cell by the afternoon), but in general, six-cell to ten-cell embryos are what we are happiest with at transfer time.
- DEGREE OF FRAGMENTATION: The more cells that are broken into little chunks, the lower the chance of success. Perfect grade-A embryos have classic perfectly round, unfragmented cells.
- FROM WHOM DID THE EMBRYOS COME: This is a very important factor. An 8cA embryo from a 43-year old with 2 previous failed IVF cycles has a much lower chance of successful implantation as compared to a 6cB from a 27-year-old egg donor with 3 previous pregnancies.
So, of Terra’s original 11 embryos, 3 looked pretty good, 6 looked great and 2 were dead (degnerated).
So taking all this into account, an 8cA embryo from Terra, a healthy 30-year-old with no previous IVF failures would be considered High-Chance. My best guess was that each of those had perhaps a 40-50% chance of becoming a baby and my recommendation was to transfer two. If she absolutely refused to consider having twins, we could always just transfer one. If she wanted to take a risk of triplets, but boost her odds of success, we could transfer three. If we were in Europe, we would have no choice as the government controls how many embryos can be transferred with different countries having different guidelines. However, in the US, we have the freedom of choice to use our best medical judgment. Terra and Miles opted to be aggressive, against my recommendation and transfer three. Had they asked me to put in 4, I would have strongly advised against it and most likely, I would have even refused. But transferring three would give them less than a 5% chance of triplets in my estimate based on their entire clinical picture. Different RE’s have different preferences. I have known other RE’s who would not have transferred three, while I’ve known still others who would have transferred 6 without hesitation
!
In Terra’s case, there was yet another possibility. We could wait 2 more days and see how each of those nine surviving embryos looked then. Sometimes an embryo that looks great at day 3 can look worse on day 5 and one that looks mediocre on day 3 can look amazing on day 5. This is the whole idea between doing a day 5 blastocyst transfer vs a day 3 transfer. The advantage of doing this is the opportunity to better tell which embryos are High-Chance and which are Low-Chance. The disadvantage is that some embryos that would have made a baby had you put it safely into the mom on day 3, might die in the lab before making it to day 5. This is controversial, because some RE’s believe that any embryo that grows poorly in the lab to day 5 would have not survived anyway had you transferred into the uterus on day 3. In my opinion, this is often true, but not 100% true.
Our final decision was to stick to a D3 transfer and to transfer three embryos. The exact rationale for this decision would require a long detailed explanation. Suffice it say that the optimal choice varies greater from laboratory to laboratory. (During this particular year, the D3 results for this lab were as good as the D5 results).
I should add that we have the unique advantage of having two laboratories that we work with. I am blessed with having exclusive dual access to two of the top embryology labs in our area. I share access to one lab with 5 other RE’s and I share access to the second lab with 3 other different RE’s. A lot of my decisions on which lab to use, how many embryos to transfer and whether to day 3 or day 5 transfers depend on factors that are always changing from lab to lab and from year to year. I believe that each lab has its specific strengths and weaknesses. So the best strategy is to individualize all decisions. One obvious strategy for patients who fail a cycle at one lab is to have them try the other lab, because although one is not necessarily better than the other, one might be better for THAT particular patient. Brand A tennis racket might not be better than Brand B, but a player that doesn’t do well with racket A might excel with racket B, just as a player who doesn’t do well with racket B might excel with racket A.
In any case, I went along with Terra and Miles in their slightly more aggressive choice and I put back three embryos with a careful ultrasound-guided transfer.
I realize that just because the result is a good one doesn’t mean the decision was necessarily the best. However, Terra wound up 12 days later with a positive pregnancy!
To fast forward, two and a half weeks after that, we saw two heartbeats 
on ultrasound. Two weeks after that, one of the heartbeats had stopped. Fortunately, however, Terra went on to deliver a single baby boy. Of the remaining embryos, 4 survived to blastocyst and were frozen on day 5. Three years later, Terra returned for transfer of two of those frozen embryos and went on to get pregnant again, and have another boy. They still have two embryos safely frozen in liquid nitrogen awaiting their chance in another few years.
We still don’t know why Terra and Miles get pregnant so easily with IVF and yet don’t get pregnant on their own or even with IUI. However, this is the case for many infertile couples, for whom we don’t have a diagnosis other than unexplained infertility, but yet, we can often provide an effective cure without knowing the exact cause 
.
