Embryo Chromosome Testing (CGH)

Embryo Chromosome Screening (CGH)

Embryo chromosome screening using Comparative Genomic Hybridization (CGH) is an advanced genetic test used to evaluate the number and composition of chromosomes in embryos before implantation in the uterus during in vitro fertilization (IVF). This test aims to detect any chromosomal abnormalities that may affect pregnancy success rates or lead to genetic disorders.

Importance of Embryo Chromosome Screening (CGH)

CGH is a modern technique that helps in:

• Detecting chromosomal abnormalities, such as trisomy, including conditions like Down syndrome (Trisomy 21) and Edwards syndrome (Trisomy 18).
• Enhancing the success rate of IVF by selecting genetically healthy embryos, thereby increasing the likelihood of a successful pregnancy.
• Reducing the risk of miscarriage, as chromosomal abnormalities are one of the leading causes of recurrent pregnancy loss.
• Minimizing the chances of genetic disorders, especially for couples with a family history of genetic diseases or those who have experienced multiple miscarriages.

How is CGH Performed?

1. Embryo Biopsy: A sample of cells is taken from the embryo on the fifth or sixth day after fertilization using the biopsy technique.
2. Laboratory Analysis: The embryo’s DNA is analyzed using CGH Array or aCGH technology, where the embryo’s chromosomes are compared with normal chromosomes to check for any gains or losses in chromosome numbers.
3. Selection of Healthy Embryos: After analysis, embryos without chromosomal abnormalities are selected for transfer.
4. Embryo Transfer: The selected embryos are implanted into the mother’s uterus to continue the pregnancy process.

Types of Chromosomal Abnormalities Detected by CGH

• Numerical abnormalities: Such as Down syndrome (Trisomy 21), Patau syndrome (Trisomy 13), and Turner syndrome (XO).
• Structural abnormalities: Including deletions (missing chromosome segments) and duplications (extra chromosome segments).
• Genetic mosaicism (Mosaicism): A condition where an embryo contains cells with different chromosomal compositions.

When is CGH Recommended?

Couples may be advised to undergo this test in the following cases:

• Women over 35 years of age, as the risk of chromosomal abnormalities increases with age.
• Unexplained recurrent miscarriages.
• Repeated IVF failures.
• Family history of genetic diseases.
• Couples with balanced chromosomal translocations.