PGS (Preimplantation Genetic Screening)
4/23/2020 12:39:00 AM
PGS (Preimplantation Genetic Screening) 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.
Large deletion (≧10 Mb): Prader-Willi syndrome, Cri-du-chat syndrome, DiGeorge syndrome, Angelman syndrome, etc.
Limitation
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.