Preimplantation Genetic Screening (PGS)
Chromosomal abnormalities are one of the most common reasons for implantation failure and miscarriages that occur within the first 12 weeks of pregnancy. In fact, approximately 50-60% of miscarriages that occur in the first trimester are due to a fetal chromosomal abnormality. Chromosomally abnormal embryos may not differ in overall microscopic appearance from chromosomally normal embryos, making it difficult to identify which embryo(s) have the best chance of resulting in a healthy baby. By implanting a chromosomally normal embryo, the possibility of a successful implantation and pregnancy is significantly enhanced.
How is PGS Performed?
PGS involves testing an embryo’s chromosomes. Chromosomes are the structures inside of our cells that contain the genetic information needed for our bodies to grow, develop, and maintain our health. There are 23 pairs of chromosomes (46 total). Chromosomes 1-22 are called autosomes, and are present in both males and females. The 23rd pair of chromosomes determines whether we are male (XY) or female (XX). Changes to the number or structure of the chromosomes may cause failure of an embryo to implant, result in a miscarriage, or lead to the birth of a baby with developmental and/or physical abnormalities.
CombiMatrix utilizes a technique called Chromosomal Microarray Analysis (CMA) to evaluate the embryo for chromosomal abnormalities. By investigating hundreds of thousands of points along all 23 pairs of chromosomes, CMA is able to determine how many copies of any given region of a chromosome are present. For the first 22 pairs (the autosomes), there should be two copies of each chromosome. For the 23rd pair, there should be either two X chromosomes (female) or an X and a Y (male). When there is an extra or missing chromosome, this is referred to as aneuploidy. If there is a gain or loss of the entire chromosome, it is called a whole chromosome aneuploidy. If there is a gain or loss that involves a region greater than 30 Mb in size, it is called a segmental aneuploidy. Most implantation failures and miscarriages are caused by whole chromosome aneuploidy, however, segmental aneuploidies may have a similar effect. Because of the small sample size (one or several cells), it is not possible to identify segmental aneuploidy of regions smaller than 30 Mb in size.
Who Can Benefit From PGS?
In addition to increasing the likelihood of a successful pregnancy for any couple, PGS may benefit couples who:
- Have experienced one or more failed IVF cycles
- Have a history of recurrent miscarriage
- Prefer to have a single embryo transferred
- Have had a previous pregnancy or child with a chromosomal abnormality
- Are at increased risk for aneuploidy due to advanced maternal age
Click here for our PGS Patient Brochure
If you are considering PGS, please speak to your fertility specialist for more information. If you and your fertility specialist have decided that PGS is the right decision for you, please click here to complete the PGS Consent Form and PGS Authorization Form.