Embryo Grading

Embryo grading

Embryo Grading


What is Embryo Grading?

Embryo Grading is done to make sure that you have a better success rate of conceiving through IVF, it is important that only the best quality embryo is selected for transfer. The remaining good quality embryos are frozen and stored. They are used if the first embryo transfer is not successful.

PROCESS OF EMBRYO GRADING: During fertilization inside a female's body, the egg gets fertilized by sperm in the fallopian tube and an embryo is formed. The embryo usually takes 5 or 6 days to reach the uterine cavity after fertilization. At this time an embryo made up of hundreds of cells is created from a fertilized egg.  A blastocyst In an IVF cycle forms in a culture system in a laboratory.  Eggs are taken from a woman's ovaries, fertilized with sperm, and an embryo is created.

When are embryos transferred?


Embryos are transferred into your womb at different stages of their development that are decided on the basis which embryo can give the best success rate of pregnancy.

Embryos can be selected on various days accordingly. Sometimes embryos are selected on day 2 or 3 of their development also known as cleavage stage embryos.

They can also be selected on other days, to develop more for 4 - 5 days until they reach the blastocyst stage.

Embryo transfer is a hard decision to make, so Embryologists use their experience & training to assess embryos and select those who may give the best success rate. Embryologists apply a system of Embryo grading, using the following criteria for early stage embryos such as:

The number of cells presents in the embryo.

  • How fast the cells are getting divided. 
  • The cell division is even or not.
  • There are any fragments of cells present.

Embryo Grading



Day 3 Embryo Grading:


Day 3 embryos or cleavage stage embryos. In this stage, the cells in the embryo are dividing, but the embryo is not growing. The genetic material gets replicates, and the cells get divided, but the volume of the embryo is same as the volume of the unfertilized egg.

The Embryos do not divide synchronously there may be three, five, six cell, etc. embryos. This doesn't mean it is a poor embryo, but of one that is growing normally. Sometimes during embryo division, a small portion of cytoplasm breaks and form a blob that also called as a fragment. Too much of fragmentation are developmentally disadvantaged because the cells lose too much of cytoplasm. This is all about Day 3 embryo grading.

Cleavage stage embryos gets graded using the following criteria: 


The appearance of the cells and the number of cells in the embryo. A good growing day three embryos will contain between six and ten cells. The embryo grade means how the cells in the embryos look. 

Embryo Grading - Description


Grade 1 -  Equal size of cells and have no fragmentation is seen
Grade 2 - Equal size of cells and have minor fragmentation only
Grade 2.5 - Mostly cells are of equal size and have moderate fragmentation
Grade 3 -  Cells are of unequal size and have no fragmentation or moderate fragmentation
Grade 4 - Equal or unequal size of cells and fragmentation is moderate to heavy

Grade 1 to Grade 2.5 embryos have the greatest potential for developing to the blastocyst stage. A grade three embryo may also be of good quality if its appearance is not explained by poor development and is explained by asynchronous cell division.

Day 5 Embryo Grading:


Embryos continue to divide, and the number of cells keeps on increasing, but the cells also grow and different into specific cell types. 

There is two type of cells in the day five embryo. One cell type forms the (ICM) Inner Cell Mass. This ball of cells will grow into the fetus. 

Another cell type is the (TE) Trophectoderm Epithelium. 

These cells will go on to make tissues needed during pregnancy. Together these cell types make a fluid-filled sphere with the Trophectoderm Epithelium cells on the outside and the Inner Cell Mass inside. Both types of cells are necessary for a healthy pregnancy. This is all about Day 5 Embryo Grading

APPEARANCE OF EMBRYO ON VARIOUS DAYS:


  • APPEARANCE OF EMBRYO ON DAY 0 OR DAY OF EGG RETRIEVAL


Egg mass immediately follows egg retrieval process. The dark circle in the center is the egg.



  • APPEARANCE OF EMBRYO ON DAY 1 OR FERTILIZATION DAY


Embryo Grading
Normal fertilization with egg and egg with abnormal fertilization



  • APPEARANCE OF EMBRYO ON DAY 2 OR EARLY GROWTH OF EMBRYO


Embryo Grading
Good quality 4-cell embryo, with cells of slightly different sizes. There are a few fragments (the small “bubbles” seen). This is an example of a grade 2 embryo.


  • APPEARANCE OF EMBRYO ON DAY 3 EARLY GROWTH OF EMBRYO OR CAN BE A POSSIBLE TRANSFER DAY


Embryo Grading
 Day 3 Excellent quality embryo with 7 cells present. This is an example of a grade 1 embryo



  • APPEARANCE OF EMBRYO ON DAY 5 BLASTOCYST FORMATION AND EMBRYO TRANSFER


Embryo Grading
Very good quality expanded blastocyst. The “scalloped” inner edge of the blastocyst is called the trophectoderm, and the “clump” of cells at the bottom of the blastocyst is the (ICM) inner cell mass

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