PGS (Preimplantation Genetic Screening) involves using IVF techniques， to fertilize eggs and sperm in vitro and allow them to develop into embryos. When the embryo reaches the blastocyst stage on day 5–7, a biopsy is taken from the trophectoderm cells for analysis. The embryo is then cryopreserved while next-generation sequencing determines whether it is euploid. Once confirmed, the physician selects chromosomally normal embryos and arranges for thawing and transfer. Since chromosomal abnormalities are the most common cause of IVF failure, this screening increases implantation and pregnancy rates, reduces miscarriage risk, and helps prevent birth defects or genetic diseases.
Further reading
Indications for PGS:
- Advanced maternal age (≥35 years)
- Multiple failed embryo transfers
- Recurrent unexplained miscarriage
- Family history of chromosomal disorders
- Previous pregnancy with chromosomal abnormalities
Q&A
How long does it take to receive PGS test results?
It takes approximately 10–14 business days after the biopsy is sent to the lab.
If PGS testing was done before implantation, do I still need other tests during pregnancy?
Yes, because mutations may still occur during embryonic development. Although trophectoderm and inner cell mass cells are largely consistent, there can be discrepancies. This means chromosomal abnormalities in the inner cell mass may be missed. PGS does not detect microdeletions under 10MB, single-gene disorders, chromosomal rearrangements, inversions, micro-balanced translocations, mosaicism, balanced translocations, or polyploidy. Therefore, additional prenatal testing like amniocentesis or NIPT is recommended during pregnancy.
Can PGS detect inherited genetic disorders in embryos?
If either parent is a carrier or has had a child with a genetic disorder, PGT-M (Preimplantation Genetic Testing for Monogenic disorders) should be considered alongside IVF to reduce the chance of inherited conditions. For older women considering pregnancy, PGS is often suggested. However, it’s a misconception that PGS guarantees a healthy baby. All screening has limitations. Results may vary by lab or technician, so it’s important to understand what PGS cannot detect before deciding.
