Pre-implantation genetic diagnosis and trofectoderm biopsy

Pre-implantation genetic diagnosis is indicated to couples:

• subfertile/ infertile in whose reproductive history there are three or more implantation failures;
• subfertile/ infertile in whose reproductive history there are three or more spontaneous abortions, not due to mechanical/anatomical causes;
• fertile or infertile copules in which at least one of the two partners is affected by a monogenic disease, or has structural chromosomal abnormalities;
• fertile or infertile couples with a child affected by genetic disease.

The embryo at the blastocyst stage, i.e. 5-7 days after fertilization, is composed of the inner cell mass (ICM), which will give rise to the fetus, and the trophectoderm (TE), which will give rise to the placenta and embryonic adnexa. Blastocyst biopsy is performed, which consists of taking 6-10 TE cells using micromanipulation techniques. This portion of the embryo has the same genetic makeup as ICM, so the genetic analysis carried out on the fragment taken is sufficient to diagnose whether the embryo is affected, healthy carrier or not affected by a specific genetic disease. While waiting for the genetic report, the blastocyst is cryopreserved. Embryos that are euploid, i.e. without any genetic or chromosomal abnormality, can then be thawed and transferred into the uterus.