By Dr Rashmi Yogish
Infertility, as a concept, has gained acceptance only recently. Assisted Reproductive Technology is a technique that has gained momentum among couples to treat infertility. In-Vitro Fertilisation is the most common form of ART that assists with the conception of a child. It is a complex procedure involving multiple steps including Embryo Grading.
Once the treatment is started, the first step involves stimulating the ovaries followed by a trigger injection. Once ready, the egg is retrieved and semen is collected leading to fertilisation and embryo development. Embryo transfer is the next phase for which embryo grading is done to select good quality ones. This is followed by the luteal phase and then the pregnancy test completes the IVF procedure.
Transferring best quality embryos can help in minimising the risks of failure associated with IVF treatment. The embryo grading process happens at the cleavage or blastocyst stage in order to transfer the healthiest ones with the greatest chance of resulting in a successful pregnancy.
At the cleavage stage, grading includes looking at the degree of fragmentation and the number and appearance of cells. The cell number is objective, however, the appearance is graded using a scale of 1 to 4. A good and normally growing embryo may have 6 to 10 cells. The grades are used to determine the stages of fragmentation. Grade 1 is no fragmentation and the cells are of equal size, in grade 2 minor segmentation is seen, grade 2.5 is moderate fragmentation, grade 3 is when cells begin to look unequal in size and the fragmentation is negligible to moderate. Grade 4 is when the cells are of equal or unequal size and the fragmentation is moderate to heavy. Lower the grade, greater is the chance of the embryo developing and reaching the blastocyst stage. Typically, Grade 1 to 2.5 have the greatest potential to develop further. However, both cell number and grade of the embryo is considered together to reach any conclusion. Poor quality cleavage stage embryos are identified when they have few cells and a lot of fragmentation which could lead to stunted growth.
The other system of grading embryos is during the blastocyst phase, where a report is prepared based on two aspects of the blastocyst – the inner cell mass or the foetus and trophectoderm which becomes the placenta. Stage 1 to 6 are used to determine how far the blastocyst has expanded or developed. Grades are given based on the quality, i.e., A for excellent quality, B for good, C for average or fair and D for poor quality. Good quality blastocyst are expanded and they could be in stage 3 to 5. On average embryos are between grades B & C. However blastocyst grading is a complex procedure where embryos might still be developing and hence a D grade or a C may not be the final conclusion on that specific embryo.
Embryo grading is used by doctors in combination with multiple factors related to patients like their age, fertility history, etc, to determine the best day of transferring embryos. All of the patient’s history and response to the current treatment will be taken into consideration for this process.
(The writer is an obstetrician, gynaecologist and fertility consultant.)