PGD: Trends in Pre-implantation Genetic Diagnosis

What are the new developments increasing interest in PGD?

The first is that there is more laboratory expertise on growing the embryos to blastocysts (see blog on blastocyst). These are embryos that have grown not 3, but 5 days in the lab. As the embryo grows with time, the total number of cells increases from 6-8 to 30-60. Because the cell number is much higher, we can more safely remove more than on cell, maybe 3-5 cells. All of that extra DNA helps us reach much more accurate results.

The second has to do with the way we test the DNA. The DNA amplification techniques have improved, as have the techniques for identifying important areas in the DNA.

An advantage of blastocyst biopsy is that in a good blastocyst, we can tell by looking which cells will be the embryo (the inner cell mass) and which will be the placenta (the trophectoderm- thus the term trophectoderm biopsy, also called TE biopsy for short). Naturally, at the time of the biopsy, it is the placental cells we take as not to interfere with the fetal cells. Taking a few extra cells from the placenta is much less harmful than taking cells needed for the fetus.

Another advantage of performing the biopsy on day 5 is that…..

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