Glossary · Definition · v2026.3
What Is Chromosome Nondisjunction?
Chromosome nondisjunction is the failure of chromosomes to separate properly during cell division, resulting in daughter cells with an abnormal number of chromosomes (aneuploidy).
Clinical significance
Nondisjunction during egg or sperm formation is the primary cause of aneuploidy in embryos. The risk increases significantly with maternal age, particularly after age 35, as the mechanisms controlling chromosome separation in oocytes become less reliable over time.
Common confusion
Nondisjunction is not caused by IVF procedures. It is a naturally occurring biological error that IVF makes detectable through genetic testing but cannot prevent.
Related reference
Used in
This content defines terminology for educational orientation. It does not constitute medical advice.
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