Preimplantation Genetic Screening
The Colorado Center for Reproductive Medicine is pleased to offer Preimplantation Genetic Screening (PGS), a form of genetic testing that allows couples at risk for certain chromosomal or genetic disorders to have embryos tested before a pregnancy is established. PGS is performed in conjunction with in vitro fertilization (IVF).
PGS involves embryo biopsy and genetic analysis using a variety of technologies. After testing, only embryos that have the correct number of number of chromosomes or are considered “unaffected” are chosen for transfer in the IVF cycle. The genetic material of the embryo is not altered in any way during PGS.
Who should consider PGS?
PGS is not recommended for all CCRM patients. Those who may consider PGS include the following:
- Women with a history of repeated miscarriages
- Women with a previous pregnancy involving a chromosomal abnormality
- Women who have multiple failed IVF cycles
- Individuals (male or female) who are carriers of a specific genetic condition (such as cystic fibrosis)
Women 35 years of age or older
PGS Services
- PGS for chromosomal aneuploidy (a variation in the number of chromosomes, such as an extra chromosome 21 in Down syndrome)
- PGS for chromosomal rearrangements (translocations, deletions, inversions)
- PGS for single gene disorders (such as cystic fibrosis, Huntington disease, and fragile X syndrome)
It is important to note that PGS may not be available in all circumstances or for all genetic disorders.
Patients who are interested in learning more about PGS and/or meet the criteria listed above may schedule an appointment with one of CCRM’s genetic counselors. Please call 303-788-8300
PGS Technologies for Chromosomal Aneuploidy
Flourescent in situ Hybridization (FISH) – typically screens for 9 chromosomes (13, 14, 15, 16, 17,18, 21, 22, X\Y) as well as for chromosomes that are involved in the patient-specific rearrangements. A fresh embryo transfer takes place 48 hours after biopsy.
Comparative Genomic Hybridization (CGH) or Microarray based Technology – offers comprehensive chromosomal screening for all 23 pairs of human chromosomes. Embryos are cryopreserved while genetic analysis is performed on the biopsied cells. Patients return to CCRM for a frozen embryo transfer. These technologies are provided through an Institutional Review Board (IRB) – approved ongoing clinical study.
All PGS technology has an estimated accuracy of approximately 90%. This inherent 10% error rate means that there is no guarantee that the fetus will be “unaffected”. In addition, PGS cannot detect abnormalities of chromosomes or genes which are not included in the test. It also cannot detect abnormalities that are only present in some of the embryo’s cells (mosaicism). It is highly recommended that traditional prenatal diagnosis in the form of chorionic villous sampling (CVS) or amniocentesis be performed if a pregnancy is established after PGS. In the general population, there is a 3-5% incidence of birth defects or malformations.