Understanding Preimplantation Genetic Screening (PGS)
In simple terms, preimplantation genetic screening (PGS) is the term for screening an embryo to determine viability. Screening is done to look for the normal chromosome number or for a gain or loss of chromosomal material. The presence of an abnormal number of chromosome in a cell is called aneuploidy. Essentially, it is one of a number of procedures each embryo undergoes to help identify certain genetic conditions. This all takes place before implantation of the embryo.
Process of PGS
PGS is only possible in embryo created through IVF. Through the normal process, the embryo will reach certain stages of development when a few cells can be removed. A PGS procedure tests a small sample of a cell to determine whether they have:
- Euploid: the correct number of chromosomes
- Aneuploid: the wrong number of chromosomes
- Mosaic: a mix of normal and abnormal cells
However, while early detection of some conditions can be considered an advantage, there are disadvantages to testing throughout an embryo’s development.
Why screening for genetics?
Preimplantation genetic screening is all about finding out whether an embryo has too much or too little chromosomal material. When there is an abnormality in chromosomes, it can result in a number of conditions, such as Down syndrome, Trisomy 18 or Trisomy 13.
Each of these, in turn, can have other adverse effects, including:
- Intellectual disabilities
- Birth defects
Overall, the aim of a preimplantation genetic screening is to increase the chances of an IVF patient having a healthy pregnancy.
Promoting successful pregnancies
All couples are at risk of creating embryos with the incorrect number of chromosomes. The purpose of preimplantation genetic screening is to identify aneuploid cells before IVF because these embryos do not lead to successful pregnancies.
Increasing the likelihood of pregnancy
Some studies indicate that pre-implantation genetic screening can increase the likelihood that the embryo will implant. PGS is also said to reduce the rate of miscarriage and increase the likelihood of a live birth. Fortunately, there are resources for genetic counseling for patients who are considering the advantages and possible risks associated with preimplantation genetic screening.