Embryo Grading and IVF Timetable

You can ask the Lab Director (or physician) to give you progress reports on the development of your embryos. Critical points in development are (1) fertilization, (2) 4 to 8 cell stage and (3) morula to blastocyst stage.

Numeric grading systems for multicell embryos usually 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 fragmentatio

The following is an approximate timetable of events for IVF:

Day 0 Egg retrieval Sperm collection and preparation Insemination
Day 1 Check eggs for fertilization (the presence of two pronuclei or PN's)
Day 2 Embryos at the 4-cell or more stage of development
Day 3 Embryos at the 8-cell or more stage of development
Day 4 Embryos at the compacted morula (16-32 cell) stage
Day 5 Embryos at the blastocyst stage of developmen

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 is going to be the placenta).

Multicell embryos that recieve grade 1 or 2 often develop to the blastocyst stage, those receiving grade 3 or 4 rarely develop to the blastocyst stage. Sometimes the laboratory uses the reversed scale where a grade 4 embryo is equivalent to a grade 1 embryo on the above scale. Please Check with your lab.