At present it is almost imperative that the centers of Assisted Reproduction have the possibility of conducting genetic studies on embryos before being transferred to the uterus: (preimplantacional Genetic Diagnosis).

Preimplantacional Genetic diagnosis

Introduction

There are many factors that influence the viability of an embryo, but one of the most important are the chromosomal abnormalities.
Less than half of all conceptions result in a live fetus.
In IVF, many embryos fail to "progress" before being transferred.
Of those that survive and are transferred only 5-30% end in a live fetus, depending on the woman's age. More than half of human embryos after IVF cycle have cells with chromosomal abnormalities.
These embryos with abnormalities in the number or structure of chromosomes can be morphologically normal.

The selection of embryos are based on preliminary chromosomal studies using the technique of FISH:
1 .- Reduces the rate of spontaneous abortions
2 .- Reduces the incidence of aneuploidy
3 .- Increases the rate of embryo implantation

The DGP also allows the study of congenital diseases where the parents are carriers, which are a result of the malfunction or deficit of one particular gene (monogenic diseases).

Methodology:

In a conventional IVF cycle, when the embryology laboratory has embryos at the stadium in cells 6-8 (corresponding to the day 3 post-fecundation), we remove one or two cells in each embryo.
These cells pass to the biopsy genetics lab where the study of possible aneuploidy (9 chromosomes), traslocations or other structural abnormalities of chromosomes are conducted.
Whether to perform a study of translocations (investigation of chromosomal abnormalities) or a particular gene, will be technically in the same way, but prior to the start of the IVF cycle, we must perform a study of information in the pair progenitor and even, at times, in other family members.

Technical limitations:

There are technical limitations on the number of chromosomes that can be analyzed (only 9), as well as the difficulties involved in the study of a single cell.

It could happen that the embryos have no information, and we don’t know if they are suffering from the disease to be studied.

It could also happen to have no normal embryos to transfer.

At least we need a minimum of 5 morphologically normal embryos so that the technique can be carried out with maximum guarantee that the result is appropriate.

Although the technique has been successful and pregnancy follows, an amniocentesis is recommended in cases of possible anomalies in the number or structure of chromosomes, to confirm the result and discard any mosicism (some of the cells normal fetuses and some of them with anomalies).

Likewise, if the DGP has been carried out by repeated failures of implantation in IVF cycle, for maternal age, or repeated abortions, an amniocentesis is recommended.