How are the results of your pre-embryo transfer genetic screening interpreted?

Article written by Doctor Do Huy Duong - Vinmec High-Tech Center

Pre-embryo transfer genetic screening is a genetic test, performed on embryo biopsy samples to identify genetic abnormalities at the chromosomal level, thereby helping doctors select embryos with the most potential for embryo transfer. help improve the success rate of artificial insemination (IVF).

Human chromosome set consists of 46 chromosomes divided into 23 pairs. These chromosomes are inherited in pairs, with each chromosome in a pair coming from either parent. The first 22 pairs of chromosomes (ordinary chromosomes) are similar in size and shape. The 23rd pair of chromosomes is the sex chromosome pair. The sex chromosome pair XX determines the female sex; The XY pair of sex chromosomes determines the male sex.
So what do the results of genetic screening before embryo transfer say:
No abnormalities detected: That is, no genetic abnormalities were detected within the limits of the method. The results of “No abnormality detected” showed that the chromosome set of the embryo was 46 chromosomes intact. These are the embryos with the most potential to be selected for embryo transfer because of the highest possibility of implantation and development into a normal baby.

Chromosomal Abnormalities Detection: Means the detection of one or several abnormalities at the chromosomal level which may include the addition or loss of chromosomes; the addition or loss of a segment of a chromosome or may include many different types of abnormalities. There are many types of chromosomal abnormalities including:
Trisomy: an extra chromosome in a homologous chromosome pair. A good example of this type of chromosomal abnormality is Down syndrome with 3 chromosomes 21. Monosomy: loss of one chromosome in a homologous pair. Example: -7 (Monosomy) means that only one chromosome 7 is present in the cells of the specimen Add fragment: add part of chromosome Deletion: lose part of chromosome Mosaic : is a state in which cells in the same biopsy sample have different karyotypes. Insufficient quality for analysis: when the test data of a sample is not of good quality for accurate analysis of the results. These cases usually require a biopsy and repeat testing.
No DNA cloning product: the embryo's DNA cannot be cloned, so there is not enough material to perform the test.

Things to keep in mind when reading genetic screening results before embryo transfer:
It is not uncommon for you to have one or more embryos with genetic abnormalities. Although the percentage of embryos with genetic abnormalities increases with maternal age, all embryos have a baseline risk of genetic abnormalities independent of maternal age. Embryonic mosaicism is quite common and is not related to maternal age. Embryos identified without abnormalities have better implantation potential and a lower risk of miscarriage than embryos with abnormalities and mosaicism. However, some mosaic embryos also have embryo transfer potential and develop normally. The results of genetic screening before embryo transfer can sometimes be confusing. Do not hesitate to contact Vinmec genetic counselors to fully understand your results and be advised on the next steps to take.
Currently, Vinmec Times City International General Hospital is organizing the implementation of the Genetic Screening Package before embryo transfer. This is a prestigious medical address with a team of well-trained experts and technicians at home and abroad, rich in experience in the field of pre-implantation genetic screening. Vinmec has modern facilities, meeting international standards, always applying the most advanced techniques such as Microarray, NGS new generation sequencing. In addition, it also provides a comprehensive solution including genetic counseling before and after testing for customers. With outstanding advantages, Vinmec is currently one of the reliable hospitals for customers to choose when there is a need for genetic screening before embryo transfer.

References:
McKinlay Gardner RJ and Sutherland GR. Chromosome Abnormalities and Genetic Counseling, 3rd edition. Oxford, Oxford Press, 2004. CooperGenomics internal data Victor AR, et al. One hundred mosaic embryos transferredly in a single clinic: exploring when and why they result in healthy, Fertility and Sterility , 2019. 111(2): p. 280-293. Munne S., et al., Detailed investigation into the cytogenetic constitution and pregnancy outcome of replacing mosaic blastocysts detected with the use of high-resolution next-generation sequencing, Fertility and Sterility , 2018. 108(1): p. 62-71. Munne, S, et al., Clinical outcomes after the transfer of blastocysts built as mosaic by high resolution next sequencing – further insights, European Journal of Medical Genetics , 2020. 63(2): 103741.