Meet the Blastocyst

Hello everyone, this blog will describe the blastocyst. I will show you some pictures and tell you what is good and what is less good. Next time I will tell you a little about our blastocyst experience at NYU.
Let’s start with an easy one, a nice one. This is a very nice blasotocyst.


This is the type of embryo you may see on doctor’s web sites.

So what are we looking for? In no particular order, one is the thickness of the zona. This is the thin membrane around the embryo; it looks like a clear plastic shell. The thinner the better. As the embryo grows, gets larger, and becomes ready to pop out of the zona. The zona gets thinner, and this is a good sign. We don’t measure the thickness; we just look at it and make a judgment. The bigger embryo in the picture below has a really thin zona, almost impossible to see, which is a good thing.



This embryo has a much thicker zona, not as good.



What else are we looking for? We look inside the embryo. You may not be able to tell by looking right away, but the inside is hollow. Thus the name blastocyst: the inside is like a fluid filled cyst. That’s a good thing. So the next embryos have a lot of space on the inside, the cavity (the space inside) is large, another good thing.



This familiar embryo has a smaller cavity, not as good, but not a terrible embryo overall.

What about the cells of the embryo? There are 2 types. There is the inner cell mass and the trophectoderm. The inner cell mass goes on to become the fetus/baby, the trophectoderm cells go on to become the placenta. Many more cells are designated for the placenta than are for the fetus. Ideally, the inner cell mass (ICM) is easy to see as a clump of tightly bound cells more towards the center of the embryo. Here is the nice embryo we saw before with a nub of cells at about 8 o’clock. This is a good-very good inner cell mass.

These embryos have ICMs that are smaller; in fact it’s hard to see the ICM in the bigger embryo.

Next we move on to the other cells of the blastocyst, the cells that make up the outer area. These are the trophectoderm cells, troph cells for short (really sorry about all the terminology, it just goes with the territory). Cells that are more plentiful and smaller make a better embryo. The larger embryo below has very nice troph cells (and the ICM is really nice too).

This embryo has troph cells that are not quite as good: they are larger and fewer in number.

The embryo on the left below has just a few troph cells and they are really spread out, not so good.

The next embryos are not very good looking. The top left does have a cavity, and the cells are not very good. The top right has a very small cavity. The bottom embryo looks like there is no cavity.

The next embryos have cavities, but not the nice ICM cells and troph cells we have previously seen.

These embryos have thick zonas, the lower left has no cavity, and the upper right has a small cavity and few large cells inside.

This poor embryo has a nice thin zona, but just a few cells inside. The troph cell at 4:00 o’clock is just spread so thin, across almost half the embryo. The ICM at 11 o’clock is tiny.

So now you know more about blastocysts than the average person undergoing infertility. I realize that some of you are not as interested in the details, and others really use the details to get through the infertility day.
Next time I will talk a little about the numbers we assign and a little about the NYU blastocyst experience.

Thanks and see you sooner next time,

Dr. Licciardi