Embryo chromosome screening

Preimplantation Genetic Screening (PGS) is a technique used to screen for chromosomal abnormalities in embryos during in vitro fertilization (IVF). Similar to Embryonic Genetic Diagnosis (PGD), PGS aims to evaluate the number and structure of chromosomes in embryos to select healthy embryos for transplantation, reducing the risk of pregnancy failure and miscarriage caused by chromosomal abnormalities. The following is a detailed explanation of PGS:

1. Target audience: PGS is suitable for couples who wish to undergo IVF, especially older women, women with recurrent miscarriages, or couples with a family history of chromosomal abnormalities. PGS can also be used to improve the success rate of IVF and reduce the risk of pregnancy termination.

2. Process: The PGS process is combined with IVF. Firstly, using superovulation drugs to induce women to produce multiple eggs. Then, sperm and egg are fertilized in vitro to form multiple fertilized eggs. At the 6-8 cell stage of embryonic development, one or more cells in the embryo are sampled. The sampled cells will undergo chromosome screening to evaluate the normality of chromosome number and structure. Based on the screening results, select embryos with normal chromosomes for transplantation.

3. Chromosome screening methods: PGS uses various chromosome screening methods for analysis. Common methods include fluorescence in situ hybridization (FISH), whole genome amplification (WGA) combined with fluorescence in situ hybridization (aCGH/FISH), single embryo multi-channel (SNP) array, and whole chromosome single-cell sequencing. These methods can screen embryos for whole or specific chromosomal regions to evaluate chromosomal abnormalities (such as trisomy syndrome) and structural abnormalities (such as chromosomal deletions, duplications, etc.).

4. Advantages and limitations: The advantage of PGS lies in its ability to screen for chromosomal abnormalities in embryos, select embryos with normal chromosomes for transplantation, improve the success rate of IVF, and reduce the risk of pregnancy failure and miscarriage caused by chromosomal abnormalities. However, it should be noted that PGS does not guarantee successful pregnancy or the birth of a healthy baby. In addition, PGS also has a certain misdiagnosis rate and potential risk of embryonic damage. Therefore, before conducting PGS, it is recommended to consult a doctor and genetic counselor to understand its applicability, advantages, limitations, and risks.

It should be emphasized that PGS is mainly used for screening chromosomal abnormalities, and does not involve the diagnosis of monogenic genetic diseases. For couples with a family history of monogenetic diseases, embryogenetic diagnosis (PGD) can be considered to screen for specific genetic diseases.

PGS (Preimplantation Genetic Screening) and PGD (Preimplantation Genetic Diagnosis) are two techniques for genetic analysis of embryos during in vitro fertilization (IVF), but they have some differences in purpose and application:

1. Purpose:

-The purpose of PGS is to screen for chromosomal abnormalities and structural abnormalities in embryos, in order to select embryos with normal chromosomes for transplantation and reduce the risk of pregnancy failure and miscarriage caused by chromosomal abnormalities.

-The purpose of PGD is to diagnose whether embryos carry specific single gene genetic diseases or chromosomal structural abnormalities, in order to avoid transferring embryos at risk of genetic diseases.

2. Application scope:

-PGS is mainly used to screen for chromosomal abnormalities, such as chromosomal number abnormalities (such as trisomy syndrome) and structural abnormalities (such as chromosomal deletions, duplications, etc.).

-PGD is mainly used to diagnose monogenic genetic diseases such as cystic fibrosis, thalassemia, and chromosomal structural abnormalities such as balanced translocation.

3. Analysis method:

-PGS typically uses chromosomal screening methods such as fluorescence in situ hybridization (FISH), whole genome amplification combined with fluorescence in situ hybridization (aCGH/FISH), single embryo multi-channel array (SNP), and whole chromosome single-cell sequencing.

-PGD uses molecular genetic techniques such as polymerase chain reaction (PCR) or other specific analytical methods to detect mutations or chromosomal structural abnormalities related to single gene inherited diseases.

4. Application object:

-PGS is suitable for couples who wish to undergo IVF, especially older women, women with recurrent miscarriages, or couples with a family history of chromosomal abnormalities.

-PGD is suitable for couples with a family history of specific single gene genetic diseases, and it is hoped to avoid transferring embryos with genetic disease risks.

In summary, PGS is mainly used to screen for chromosomal abnormalities and select embryos with normal chromosomes for transplantation, while PGD is mainly used to diagnose specific single gene genetic diseases or chromosomal structural abnormalities to avoid transferring embryos with genetic disease risks. The application purposes and analysis methods of the two technologies in the IVF process are different.