Feb 12, 2009

So your embryo stage must match if you have more than one donor. 2pn's to 2pns, and multi's to multis, and blast to blast. Only exception is that you may have a multi if your first choice is a 2pn. I think they must culture the 2pn's to multis, but I do not know this for a fact. But it would make sense. :)

http://www.miracleswaiting.org/factsembryos.html

What is the difference between an embryo and a pre-embryo?

Embryo and pre-embryo are both terms that are used broadly to refer to all the early stages of development of a fertilized egg. The word embryo is specifically used to refer to the stage of development between implantation in the uterus and the 8th week of gestation, so some IVF clinics use the term pre-embryo when describing pre-implantation embryos. However, both words are commonly used to refer to stages of development prior to transfer to the uterus.



What is a 2PN embryo?

Male and female gametes (eggs and sperm) each have a nucleus containing DNA. Within hours after penetration by the sperm, the egg jettisons half of its chromosomes in a process called meiosis. (Sperm complete meiosis much earlier, while still in the testes.) The remaining DNA packet from each gamete is called a pro-nucleus. For a period of time after the sperm penetrates the egg, the two pro-nuclei exist separately within the cytoplasm of the egg. Appropriately, this earliest stage of development is called the “two pro-nucleate” (or 2PN) stage. When embryos are being created in an IVF laboratory, the embryologist typically will be looking for proof of initial fertilization (2 pronuclei in close proximity to each other) about 16-18 hours after insemination.

http://www.miracleswaiting.org/factsembryos.html#top

What is a Zygote? What are Blastomeres?

Gradually, the two pro-nuclei gravitate toward each other, their cell walls dissolve, and they complete the process of fertilization by merging to form one nucleus. The fertilized egg is now called a “zygote.” The nucleus begins to duplicate itself by dividing into cells called blastomeres. This process is called mitosis. At first, the blastomeres are rather large, but each division produces smaller and smaller blastomeres. Normally, embryos reach the 2-4 cell stage about 24 hours after fertilization (two days after egg retrieval), and a day later, they will have about 8 cells. Here in the United States, Day 3 is the earliest stage at which embryos are routinely transferred to the uterus. In between fertilization and the point at which there are too many cells to count, they are called cleavage-stage embryos. They are also commonly referred to as 6-cells, 8-cells, etc., according to their stage of development.



What is a Morula?

When the embryo reaches about 16-32 cells, it is called a morula (mulberry shaped).

What is a Blastocyst?

As the morula continues to divide, it forms an outer shell of cells (the trophoblast) around a fluid-filled cavity (the blastocele) containing an inner cell mass (the embryoblast). At this point, the organism is called a blastocyst. An embryo usually reaches the blastocyst stage around Day 5, which is when it would normally be entering the uterus during a natural cycle. The trophoblast and embryoblast cells will continue to differentiate from one another as cell division continues within the blastocyst, laying the groundwork for the placenta to grow from the trophoblast, and the fetus to develop from the inner cell mass.