niPGT-A

◆What is niPGT-A?

niPGT-A is the latest non-invasive testing method in preimplantation screening, providing a gentle approach to fertilized eggs (embryos) without the need for TE cell collection.

◆Features of niPGT-A

niPGT-A is non-invasive to embryos as it does not involve the collection of TE cells, allowing for chromosomal abnormality testing without damaging the embryos compared to conventional PGT-A. The specific procedure involves retrieving culture medium from blastocysts that have grown on the 6th or 7th day after fertilization, extracting and amplifying DNA from it, and analyzing it by NGS. Blastocysts are preserved frozen until test results are obtained.

◆Advantages and Disadvantages

Advantages

• No damage to embryos
  Uses culture medium that is typically discarded, resulting in no damage to embryos.
• Precise detection of chromosomal abnormalities
  Allows for testing of chromosomal abnormalities in embryos without causing harm, reducing the miscarriage rate and shortening treatment time by pre-testing embryos used for transplantation.
• Reduction of congenital disease risk
  Potentially avoids difficult decisions during pregnancy by reducing the risk of congenital diseases.
• Improvement of embryo grade
  Allows for testing of lower-grade embryos compared to conventional methods, enabling examination of chromosomal abnormalities before transplantation.
• Increased pregnancy rates and reduced miscarriage rates
  Expected to improve the success rate of transplantation and pregnancy, reducing the risk of miscarriage.
• Gender identification
  Possible to know the gender if desired.

Disadvantages

• No effectiveness against miscarriages not caused by chromosomal aneuploidy
  Even if the test is successful, it is not effective against miscarriages not caused by chromosomal aneuploidy.

◆Testing Method

① Oocyte retrieval, Intracytoplasmic Sperm Injection (ICSI), Blastocyst culture: Oocytes are retrieved, ICSI is performed, and blastocyst culture is conducted to generate embryos.
② Collect culture medium.
③ DNA in the culture medium is amplified using PCR.
Next Generation Sequencing (NGS): The amplified DNA is subjected to chromosomal analysis by Next generation sequencing (NGS).

◆Test Results

The analysis results of NGS show the number of autosomes from 1 to 22 and sex chromosomes (X chromosome, Y chromosome). The results are plotted on a graph, with a blue line indicating trisomy (three chromosomes) and a red line indicating monosomy (only one chromosome). Normally, there are two autosomes each, and if there are no chromosomal abnormalities, they are plotted in a straight line along the baseline.
As an example, in the above test result, there is one less chromosome 16, which is expected to have a positive effect on implantation rates by excluding candidates for transplantation.
Result Example: Monosomy16, [45,XX,-16]

◆Points to Note

As of 2023, there is ongoing worldwide debate regarding the consistency of multiples between ICM biopsy or TE biopsy and the corresponding SCM of the same embryo, with no clear empirical evidence available.
Always consider false positives and false negatives.