PGS or Preimplantation genetic screening is used to denote as testing for overall chromosomal normalcy in embryos. It does not look for a specific disorder or disease. It is screening the embryo for normal chromosome copy number by using PGD techniques to identify risk. Humans have 23 pairs or 46 total number of chromosomes. Down syndrome has an extra chromosome 21 or also known as trisomy 21, This is detected by PGS. Preimplantation genetic screening helps IVF physicians and patients decide which embryos to transfer for the best success rate. Ypu can also check our article about embryo tansfer.


Now you know about PGS (Preimplantation Genetic Screening) testing but you must know what PGD (Preimplantation genetic diagnosis) is.


PGD also termed as Preimplantation genetic diagnosis is a procedure of removing a cell from an IVF embryo before being transferred to the uterus to help identify a specific genetic defect. It can also be said as genetic profiling of embryo or sometimes even of oocytes before fertilization or to check and prevent a certain disease or disorder from being passed on to the child. 

Embryos of many people are chromosomally abnormal. The rate of abnormalities is greatly affected by women's age. Chromosomes in eggs from the older female has increased the rate of abnormalities. Chromosomal abnormalities are also responsible for the failure of implantation of embryos in IVF procedure. Chromosomal abnormalities are also responsible for about 70% of miscarriages in early pregnancy.

Preimplantation genetic diagnosis or PGD involves the following steps:

  • A cell is removed from the embryo.
  • The cell is then evaluated to determine problematic gene is present in the embryo.
  • After the PGD procedure has been performed and identification of genetic problems free embryo has been done, the embryo is placed back into the uterus.
  • Additional embryos that are also free of genetic problems may be frozen for other attempts of IVF in the case of IVF process failure. 

Who can benefit from PGS?

Preimplantation genetic diagnosis can benefit couples at risk for passing on a genetic disease or condition.

  • Couple suffering from of sex-linked genetic disorders.
  • Couple suffering from of single gene disorders.
  • Those with chromosomal disorders.
  • Female above age of 35 and over.
  • Female experiencing recurring pregnancy loss
  • Female with more than one failed fertility treatment
  • Preimplantation genetic diagnosis is also used for the purpose of gender selection.
  • Men with low sperm count.
  • Females with a previous pregnancy with chromosomal abnormality


How does PGS work?

  • While undergoing IVF or ICSI treatment to collect and fertilize your eggs
  • Embryologist removes one to two cells from the embryo.
  • The chromosomes are examined to check the number of chromosomes and their normality.
  • Than embryo or embryos (depending on the situation) without abnormal numbers of chromosomes are transferred to the womb so that they can develop. 
  • Embryos that has abnormal chromosomes are allowed to perish.

Benefits of PGD?

  • Preimplantation genetic diagnosis can be used to test for more than 100 different genetic conditions.
  • Preimplantation genetic diagnosis is performed before implantation thus allowing the couple to decide if they wish to continue with the pregnancy.

Risks related to PGS?

  • Risks of fertility treatment
  • Embryos may get damage while removing cell
  • There may be chances that no embryo is suitable for transfer to the womb after Preimplantation genetic screening.
  • A miscarriage can occur even though PGS has been carried out before embryo transfer. 

With the help of advanced genetics technologies, we can do the assessment of all 23 pairs of chromosomes. There are currently four technologies that can be utilized for assessment of normality of all 23 chromosomes:

  • (NGS) Next Generation Sequencing
  • (aCGH) Array Comparative Genomic Hybridization
  • (SNP) Single nucleotide polymorphism microarrays
  • (qPCR) Quantitative real-time polymerase chain reaction

Cost of PGD - PGS

Preimplantation Genetic Screening costs in the US ranges from about $4000 TO $9000 plus all other associated IVF costs fo that you can check our article about COST OF IVF.
Sometimes PGD costs also include embryo biopsy procedure itself and costs for performing the chromosomal analysis on the cells in the genetics laboratory.

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