PGS/PGT-A (Preimplantation Genetic Screening)

PGS (Preimplantation Genetic Screening)/PGT-A is an examination for testing if there are any chromosomal abnormalities of the embryo prior to transferring. Utilizing the most advanced Next Generation Sequencing(NGS) technique, PGS are used to detect if there is any extra or missing copies of 23 pairs of chromosomes, deletion of large-DNA segment (≧10 Mb) and unbalanced translocation. The process of PGS will first start from performing the biopsies of each embryo. These biopsies would be undergone whole genomic amplification. The library of the embryos would be created by bio-molecular approaches and sequenced. The data would be interpreted by an internal software, which illustrate if there is any chromosome abnormality comparing with normal 46 chromosomes. Better than traditional array comparative genomic hybridization (aCGH) platform, PGS acquire advantages including rapidity, high level accuracy and high level sensitivity.

Having a healthy baby is the expectation of every parent. PGS allows us to examine chromosomes of the embryo and to select a normal embryo before transfer. Which not only increase the implantation rate and pregnancy rate but also reduce the probability of early miscarriage.

Who should consider doing PGS?
  • Female who is over the age of 35 years old.
  • Female who has experienced miscarriages for more than 2 times.
  • Multiple unsuccessful IVF treatments.
  • Inherited chromosomal abnormalities or chromosomal translocation.
  • Severe male infertility.
The process of PGS
  • Evaluation and consultation.
  • Signing the PGS consents after the limitation and risk of PGS are fully explained.
  • Start entering the IVF treatment. The operation of oocytes retrieval would be at around day 12-14 of the period.
  • Embryologists will fertilize the oocytes on the date of oocytes retrieval.
  • After in-vitro culture for at least 5-7 days, the blastocysts will be graded and undergone biopsy.
  • The biopsies would be sent to examination (which will take around 7-10 working days).
  • Selecting the euploid embryos to transfer.
What disease could be examined by PGS?

Aneuploidy: Down syndrome, Turnur syndrome, Klinefelter's syndrome, Edwards syndrome, Patau syndrome, etc.
Large deletion (≧10 Mb): Prader-Willi syndrome, Cri-du-chat syndrome, DiGeorge syndrome, Angelman syndrome, etc.


Although this test has a high level of accuracy, limitations are still present in current science and technology. PGS cannot be used to examine single gene mutation disease (ex. Thalassemia, Muscular dystrophy, Hemophilia), short DNA deletion, balanced translocation and polyploid. Therefore, high-level prenatal checks should still be done during pregnancy. Amniocentesis is recommended between 16 to 20 weeks of pregnancy.