IVF Timetable and Embryo Grading

by T Timothy Smith, PhD

The following is an approximate timetable of events for IVF:

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 fragmentation

Blastocysts are graded differently with 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 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. Check with your lab.

It is unusual to be allowed to go into the IVF laboratory to view your embryos in person since the lab is a sterile room like an operating room. Special clothes, hats, gloves, shoe covers etc., are required. These are not usually supplied to the patients, just lab personnel. You can, however, ask for a picture of your embryos as many labs document the embryo development with photographs or video images. Ask the Lab Director what the policy is. When you see the picture, ask for an interpretation, embryo stage, grades etc.