What is the Difference Between PGD and PGS?
PGD and PGS are both genetic screening techniques for embryos, used when couples undergo IVF. However, PGD and PGS are used for different reasons.
Preimplantation Genetic Testing (PGD & PGS)
What is the Difference Between PGD and PGS?
PGD and PGS are both genetic screening techniques for embryos, used when couples undergo IVF. However, PGD and PGS are used for different reasons.
PGD (Preimplantation Genetic Diagnosis):
- Screens single cells from embryos for single-gene genetic diseases and chromosomal disorders before a pregnancy. PDG lets at-risk couples select the embryos most likely to create healthier, disease-free babies.
- To perform PGD testing, a single cell is biopsied from each viable embryo around day 5 of embryo development. These cells are sent to a specialized genetics lab where the screening is performed.
- All embryos are cryogenically frozen while we await the results of PGD. The results of the screening will identify which embryos are free of genetic abnormalities. These embryos have the highest likelihood of developing into a healthy, full-term pregnancy and live birth.
PGS (Pre-Implantation Genetic Screening):
- Screens embryos before implantation using technology from PGD to reduce miscarriage rates and implantation failures. PGS is also known as Comparative Chromosome Screening.
- PGS also uses one or two cells from an embryo biopsy to perform testing.
- PGS testing looks at an embryo’s chromosomes and identifies when there are an appropriate number present. Each partner contributes 23 chromosomes to a normally developing embryo meaning a healthy embryo has 46 chromosomes.
- PGS provides additional guidance to the embryology team by identifying which embryos are chromosomally normal.
How Does PGD Improve Pregnancy Rates
PGD improves pregnancy rates by identifying the presence of certain kinds of genetic disorders which can seriously affect the health of a baby. PGD helps with early detection of the following conditions:
- Chromosomal Translocation or the rearrangement of parts of chromosomes. Chromosomal translocation can be balanced or unbalanced. Balanced translocation can lead to no complications for the developing embryo, although some balanced translocations lead to general infertility later in life. Unbalanced translocation can lead to failed implantation, miscarriage, or a host of physical and mental disorders in a full term birth.
- Genetic Disorders that are the result of a single mutated gene. There are over 4,000 single mutated gene disorders. The most common we test for are Cystic Fibrosis, Tay Sachs, Fragile X, Myotonic Dystrophy and Thalassemia.
Who is a candidate for PGD?
PGD can be beneficial if your or your partner:
- Are known carriers of any single gene genetic disorder
- Have, or are a carrier for, a chromosomal disorder such as Down’s syndrome, Turner’s syndrome, XXY, and Edward’s syndrome.
- Women greater than 35 years old
- Women with recurrent miscarriages
- Women who have had a failed IVF cycle
What Conditions Does PGS Screen?
A healthy embryo has 46 chromosomes and PGS can identify embryos with aneuploidy—missing or additional numbers of chromosomes. Aneuploidy is a leading cause of miscarriage and implantation failure. By ruling out embryos with chromosomal abnormalities, doctors can transfer only those with the greatest chance of success. This allows us to recommend single embryo transfers with greater confidence. Transferring a single embryo eliminates the potential for complications present when carrying multiples. Not every patient undergoing IVF needs PGS. PGS is recommended for patients who:
- Experienced multiple unexplained miscarriages.
- Are 35 or older. As we age, a woman’s eggs become increasingly likely to have a chromosome abnormality. By 35, nearly 50% of your eggs are aneuploid. By 40, this has increased to 70%.
What Conditions Does PGS Screen?
A healthy embryo has 46 chromosomes and PGS can identify embryos with aneuploidy—missing or additional numbers of chromosomes. Aneuploidy is a leading cause of miscarriage and implantation failure. By ruling out embryos with chromosomal abnormalities, doctors can transfer only those with the greatest chance of success. This allows us to recommend single embryo transfers with greater confidence. Transferring a single embryo eliminates the potential for complications present when carrying multiples. Not every patient undergoing IVF needs PGS. PGS is recommended for patients who:
- Experienced multiple unexplained miscarriages.
- Are 35 or older. As we age, a woman’s eggs become increasingly likely to have a chromosome abnormality. By 35, nearly 50% of your eggs are aneuploid. By 40, this has increased to 70%.
Schedule a Consultation
These diagnostic technologies can provide a much higher degree success for patients who fit the criteria, but determining which test to perform and when to perform it can be a difficult decision. We would love the opportunity to discuss PGD and PGS with you in person. Schedule an appointment with one of our physicians and or email Aspire with any questions. We invite you to learn more about our locations, get five-star patient support or request an appointment to get started.
