Preimplantation genetic screening (PGS) using next generation sequencing (NGS) has revolutionized the world of infertility treatment. Once fertilization and several days of growth have occurred, embryos created via IVF are ready to be transferred. While embryos are generally graded on their size, shape, and appearance, research has shown that genetic makeup can be a key indicator when determining an embryo’s chance of successfully implanting. PGS is a test that helps determine if an embryo has a normal amount of chromosomes before being transferred to awoman’s uterus.
What Does PGS Test For?
Preimplantation genetic screening has been shown to significantly increase a woman’s chance of getting pregnant. When a doctor is able to identify the healthiest embryo(s) to transfer, the chance of a successful pregnancy increases by up to 30 percent.
A normal embryo contains 46 chromosomes that are inherited by both parents during the fertilization process. The sperm contributes 23 chromosomes and the egg contributes an additional 23. When an embryo is found to have an abnormal amount of chromosomes (too many or too few), it is known as aneuploidy which is known to cause failed pregnancies and birth defects.
By identifying embryos that have the correct number of chromosomes through preimplantation genetic screening, couples can increase their odds of implantation, reduce their risk of miscarriage, and lessen their chance of having a child with a genetic disease. The most common conditions caused by chromosome abnormalities include Down syndrome, Klinefelter syndrome, and Turner syndrome.
Who Is a Good Candidate for PGS?
Screening embryos prior to implantation can result in higher implantation rates and fewer losses during pregnancy. However, certain factors make some couples better candidates than others when determining if genetic testing is necessary.
Advanced maternal age (over 35 years old) can affect the quality of a woman’s eggs (oocytes) leading to chromosomal abnormalities. Women who have had failed IVF cycles may also be good candidates for PGS. Patients who have a history of recurrent miscarriages or have been diagnosed with recurrent pregnancy loss (RPL) may also benefit from genetic testing.
What Is Next Generation Sequencing?
Next generation sequencing (NGS) is the latest genetic screening test available to couples who are undergoing IVF treatment. This new technology is a method of PGS used for the comprehensive testing of embryos for chromosomal abnormalities. With NGS, doctors are able to look for defects with a higher accuracy compared to other genetic testing methods. Next generation sequencing can be used in conjunction with PGS or ran as a stand-alone test.