Preimplantation Genetic Diagnosis (PGD)

What is the preimplantation genetic diagnosis?

Genetic Diagnosis preimplantation (PGD), can detect genetic abnormalities in an embryo in vitro fertilized before transfer from the laboratory to the uterus.

The process consists of taking a biopsy of an embryo cell (blastomere) on the third day and submitting it to several genetic anomaly detection tests. This is a specialized procedure performed by qualified professionals under a powerful microscope, using a hollow glass needle to penetrate the outer cover of the embryo and eliminate a single cell.

Cell chromosomes are studied to determine the presence of damage or any other problem that may adversely affect pregnancy, which may report on what other fertility treatments to use, or even reveal factors previously. Strangers who have led to repeated loss of pregnancy or infertility.

The genetic diagnosis Preimplantation is recommended for couples with a history of miscarriage, two or more failed implementations of IVF/ICSI, previous pregnancies with trisomy or monosomías or patients over 40 years. It can also help to reassure your developing embryo is healthy.

PGS (Preimplantation Genetic Screening)

Preimplantation genetic screening (PGS) for aneuploidy is a powerful genetic test that may be performed on embryos during IVF treatment to screen for numerical chromosomal abnormalities

Alterations in the chromosome endowment can lead to failure of implantation in cycles of assisted reproduction, spontaneous abortions and chromosomopathies in newborns.

The PGS for chromosomal abnormalities allows to select those chromosomally normal embryos of all the evolutionary embryos of a patient, which increases their reproductive possibilities.

Embryos that are chromosomally normal are more likely to evolve properly and result in a healthy child.

PGS offers comprehensive analysis of all 24 chromosome types: the two sex chromosomes (X and Y) and the 22 other non-sex chromosomes. Normally there are 23 pairs of chromosomes in each human cell. A numerical change in the number of chromosomes is called aneuploidy. Aneuploidy is responsible for the vast majority of spontaneous miscarriages and can result in birth defects and mental retardation in

Aneuploidy is responsible for the vast majority of spontaneous miscarriages and can result in birth defects and mental retardation in live born babies. Most types of aneuploidy are not compatible with life. The most common syndromes caused by non-sex chromosome aneuploidies are Down syndrome, Edwards syndrome, and Patau syndrome. Aneuploidy is usually not inherited and can involve any chromosome; however, the likelihood of embryos being aneuploid increases with the age of the mother.

Who should use PGS testing?

Over 50% of spontaneous miscarriages are caused by chromosomal abnormalities. Some birth defects are caused by chromosome abnormalities, and the risks of having a child with a chromosome abnormality increases with maternal age. Couples who are at increased risk of having aneuploidy embryos should consider using PGS testing. These groups of individuals include:

Women over 35 years of age

Couples who have experienced several spontaneous miscarriages of unknown cause
Couples with several cycles of IVF that have not achieved pregnancy
Men with low sperm concentration
Couples with a previous pregnancy with chromosomal abnormality
The selection of chromosomally normal embryos in these couples greatly reduces the risk of miscarriage and increases reproductive success.

Delayed Maternity (Advanced Maternal Age)

he rhythm of life has caused more and more women to decide to become mothers later in life when their fertility has been reduced. A woman is born with a certain number of eggs, and her ability have children decreases over her lifetime, in part because the chance of chromosome abnormalities also increases as she ages. Most embryos with an incorrect number of chromosomes fail to implant or miscarry during the first trimester of pregnancy. The decline in fertility is gradual, but many medical providers consider the risks of chromosome abnormalities to be significant at age 35 or older. Chromosome abnormalities in live borns can cause conditions such as Down syndrome (three copies of chromosome 21 instead of two), Edwards syndrome, and Patau syndrome.

Does PGS include all genetic diseases?

No genetic test can detect all potential genetic abnormalities. PGS testing for aneuploidy can only assess numerical changes in chromosome number and other imbalances in genetic material including deletions and duplications. PGS will identify any missing or extra chromosomes, deletions, duplications, and unbalanced rearrangements that are larger than our detection limit of 6 Mb. PGS for aneuploidy screening cannot rule out single gene disorders, balanced structural abnormalities, uniparental disomy, and genetic imbalances including deletions and duplications smaller than our detection limit of 6 Mb. PGS can detect some types of polyploidy but cannot detect polyploidy in which the sex chromosomes are found as a multiple of normal (triploidy 69,XXX and tetraploidy 92,XXXX or 92,XXYY).

How many embryos are expected to be normal when using PGS?

The likelihood that embryos will be chromosomally normal decreases as women get older. According to data generated at Igenomix, the average percentage of normal embryos are:

Maternal Age (years) %Normal Embryos
30-34 60%
35-39 40%
40+ 20%

These estimates are based off of a large data set from many combined PGS cases and may not apply to small numbers of embryos from a single PGS case. Igenomix cannot guarantee that there will be normal embryos for any PGS test.