CNVs are segments of DNA that are duplicated (extra copies) or deleted (missing copies) compared to normal population. These changes can range in size and may affect one or multiple genes.

Some CNVs are inherited from parents, while others occur spontaneously (de novo) during the formation of egg or sperm cells.

Did you know?

CNVs account for approximately 12% of the human genome, far more than single nucleotide variants (SNVs).

Most CNVs do not cause any health issues. However, some can alter gene dosage, disrupt gene regulation, or change how genes interact. Depending on which genes are affected, CNVs may lead to:

• Neurodevelopmental disorders such as autism spectrum disorder (ASD), intellectual disability, or developmental disorders.
• Congenital anomalies, including heart defects or facial malformations.
• Reproductive challenges, including recurrent pregnancy loss or abnormal prenatal screening results.

The same CNV can have different effects in different people, even within the same family, a concept known as variable expressivity.

Modern genetic testing technologies have revolutionized CNV detection:

Chromosomal Microarray Analysis (CMA):

The first-line test for unexplained developmental delay, congenital anomalies, or autism.

Whole Exome Sequencing (WES) and Whole Genome Sequencing (WGS):

These methods detect CNVs alongside smaller gene mutations, providing a comprehensive view of the genome.

Prenatal Genetic Testing:

CNVs can also be detected during pregnancy through invasive procedures like chorionic villus sampling (CVS) or amniocentesis, followed by microarray analysis.

When a CNV is identified, the result isn’t always straightforward. Not all CNVs are harmful, and sometimes their significance remains uncertain. This is where genetic counseling becomes vital.

Your genetic counselor helps you understand:

• Whether the CNV is pathogenic (disease-causing), benign, or of uncertain significance (VUS).
• The inheritance pattern, whether it’s new (de novo) or inherited from a parent.
• The implications for your health, your child’s health, or future pregnancies.
• Available options for testing family members and reproductive planning.

Counselors also provide emotional and psychological support, helping families navigate uncertainty and make informed decisions based on medical evidence and personal values.

Did you know?

Chromosomal microarray testing has increased the diagnostic yield for unexplained developmental disorders by 15–20%, significantly improving outcomes for families seeking answers.

In prenatal settings, CNVs can explain abnormal ultrasound findings or atypical results from non-invasive prenatalscreening (NIPS).

• Pathogenic CNVs may indicate a high risk for structural or developmental disorders.
• Benign CNVs usually require no intervention.
• Variants of uncertain significance (VUS) are handled carefully, often requiring follow-up testing and genetic counseling to avoid unnecessary anxiety.

Couples identified as carriers of CNVs can benefit from preconception or prenatal counseling to assess reproductive risks and explore options like preimplantation genetic testing (PGT) during IVF.

Copy Number Variations represent one of the most important frontiers in genetics today. With advances in testing, families can now uncover the underlying causes of complex conditions once considered “undiagnosable.”

Genetic counseling illuminates the path through reproductive challenges, transforming uncertainty into informed action. By identifying genetic contributors, guiding targeted testing, and supporting emotional needs, counselors empower couples to make confident decisions.