The following are approximations because it can vary from patient to patient and clinic to clinic. Note that individual fertility clinics may use their “own” specific embryo grading system.

What happens on day 0? This is your egg retrieval day! While the eggs are being retrieved, sperm will be collected and prepared for fertilization.

What happens on day 1? Your eggs will be checked for fertilization. (The embryologist will be looking for the presence of two pronuclei or PN’s)

What happens on day 2? You embryos that have successfully fertilized should be at the 4-cell or more stage of development.

What happens on day 3? Your embryos should be at the 8-cell or more stage of development. (Keep in mind, not all embryos will continue to “make it” through each phase of the cell division and development process.) You may have an embryo transfer (ET) on this day.

What happens on day 4? Your embryos will be compacted morula (16-32 cell) stage. You may have an embryo transfer (ET) on this day.

What happens on day 5? Embryos at the blastocyst stage of development. You may have an embryo transfer (ET) on this day.

See if it is possible to speak with your embryologist or physician about the progress and development of your embryos. Many labs will contact you throughout the process to keep you up to date on the progress of your embryos.

The most important stages in development are:

1. Fertilization
2. 4 to 8 cell stage
3. Morula to blastocyst stage

Numeric grading systems for multicell embryos typically have 4 levels:

Grade 1: even cell division, no fragmentation
Grade 2: even cell division, small fragmentation
Grade 3: uneven cell division, moderate fragmentation
Grade 4: uneven cell division, excessive fragmentation

Blastocysts Grading – a number and two letters:

The number refers to the degree of expansion of the blastocyst (1 is the least expanded, 6 is the most expanded). The first letter (A, B, or C) refers to the quality of the inner cell mass (the part of the blastocyst that is going to be the baby) and the second letter (A, B, or C) refers to the quality of the trophectoderm (the part of the blastocyst that will become the placenta).