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What will good quality embryos look like after ICSI?


What will good quality embryos look like after ICSI?

Many of you who are undergoing treatment for infertility may be wondering whether What is the ICSI process?

ICSI process It is a process in which scientists select good quality egg cells and sperm. Injecting sperm directly into the egg cell. After that, the embryos will be cultured to grow into embryos that are ready to be transferred back into the uterine cavity. The embryo grows for about 5-6 days or what we call the blastocyst stage.

Day 1 of embryo 

What are the characteristics of a successfully fertilized embryo after ICSI?

  • A normal fertilized egg has 2 pronuclei (2PN) and 2 polar bodies.
  • Cytoplasm is usually granular, with a clear halo on the outside. On the inside there are clusters of mitochondria that appear more granular. When an egg is not fertilized, the cytoplasm is uniformly smooth.

What is 2PN?

  • PN stands for Pronuclei; After fertilizing the sperm with the egg by performing ICSI at 16-18 hours, when the egg is fertilized, two round pronuclei, called “2PN”, will be observed, one of which will come from the mother. and one from father.

Good quality 2PN embryo characteristics

  • 2PN is located in the middle of the egg and the two PNs are close to each other. See the boundaries clearly.
  • Pronuclei (PN) contain small spherical granules called “Nuleolar precuesor bodies” (NPB). Normally, each PN contains 2-7 NPBs. Both 2PNs should have a similar number and arrangement of NPBs. side by side.

Picture of Day 1 embryo (2PN)

Day 3 of embryo 

What grade should a Day 3 embryo with good development have?

  • Normal embryos develop into 4 cells on Day 2 and 8 cells on Day 3. Therefore, a good embryo on Day 3 should have 8 grade 2 cells or more.

What does each letter of the embryo grade indicate? What is it measured from?

  • Embryo development at Day 3 can be found in both the Cleavage and Morula stages, and the two stages are evaluated slightly differently.

Cleavage stage embryo quality assessment

Evaluated by number-size of cells (stage-specific size) and amount of cell debris (fragmentation) in reporting results in this phase will consist of The number of embryo cells is followed by the grade of the embryo, such as 8 cells, G.1 or 6 cells, G.2, etc., divided into 4 grades: Grade 1, Grade 2, Grade 3, and Grade 4.

  • Grade 1 (G.1) means the embryos are of very good quality, stage-specific size, and have fragmentation <10%.
  • Grade 2 (G.2) means the embryos are of good quality, most are stage-specific size and have 10-20% fragmentation.
  • Grade 3 (G.3) means the embryo is of fair quality. Most cell sizes are different and have 20-50% fragmentation.
  • Grade 4 (G.4) means embryos are of poor quality, do not have a stage-specific size, and have fragmentation >50%.

Example picture of embryo evaluation at the Cleavage stage

Morula stage embryo quality assessment

Morula stage: In this stage, the cells of the embryo will join together (Compaction) and can be divided into 3 stages:

  1. Compacting: The embryo's cells begin to join together. But cell boundaries can still be observed.
  2. Compacted: Embryonic cells are completely joined together; individual cell boundaries cannot be separated.
  3. Early cavitating: Cavities begin to appear inside the embryo. and will develop into the Blastocyst stage. Next in reporting results of this stage will include The larval stage is followed by the larval grade such as  Compacted, G.1 , Compacting, G.2 etc.  Divided into 3 grades: Grade 1, Grade 2, Grade 3.
  • Grade 1 (G.1) means the embryo is of good quality, has ≥16 cells, and the cells are joined together (Compaction).
  • Grade 2 (G.2) means the embryo is of fair quality, but compaction has not yet completely occurred.
  • Grade 3 (G.3) means the embryo is of poor quality. There are few cell connections.

Example picture of embryo evaluation at the Morula stage.

Day 5-6 of embryo 

What grade should a well-developed Day 5-6 embryo have?

  • Embryo Day 5-6 Blastocyst stage consists of Inner Cell Mass (ICM) which will develop into a child and Trophectoderm (TE) which will develop into a placenta. Therefore, for well-developed blastocyst stage embryos, the grade of ICM and TE should be grade A or B.

What does each letter of the embryo grade indicate? What is it measured from?

  • Blastocyst embryos are graded according to the size of the embryo by looking at the amount of water in the embryo's cavity or Blastocoel. From the Early Blastocyst stage to the Hatched Blastocyst stage, the amount of Blastocoel will increase according to the size of the embryo.
  • Most embryo grading today uses the Gardner system, which is embryo size grade first, followed by ICM and TE grades.

Grading embryo stages into numbers 1-6 according to the size of the embryo:

  • Grade 1 Early Blastocyst is the smallest embryo.
  • Grade 2 Blastocyst
  • Grade 3 Full Blastocyst
  • Grade 4 Expanded Blastocyst
  • Grade 5 Hatching Blastocyst
  • Grade 6 Hatched Blastocyst is the largest embryo.

ICM grades are letters A through C, with A grade being considered the best.

  • ICM Grade A means there are a lot of cells and are tight.
  • ICM Grade B is cells loosely stuck together.
  • ICM Grade C means very few cells, difficult to differentiate from TE.

TE grades are letters A through C.

  • Grade A TE is small, uniform cells in a continuous arrangement.
  • TE Grade B means fewer cells. The arrangement is discontinuous or there are gaps.
  • TE Grade C means a small number of cells. There are small and large cells.

 

 

Piyarat Sopaboon, Clinical Embryologist

Sakawprai Bamrunguom, Clinical Embryologist

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