Down Syndrome (Trisomy 21) is one of the most common genetic chromosomal disorders worldwide. It occurs when a person has a full or partial extra copy of chromosome 21. This extra genetic material affects normal development, leading to characteristic features, developmental delays, and sometimes health complications.
Here are some important facts you should know about Down Syndrome:
Key Facts About Down Syndrome
Cause: Presence of a full or partial extra chromosome 21 (Trisomy 21).
Incidence: Affects approximately 1 in 800 live births worldwide.
Pregnancy Outcome:
About 60% of affected pregnancies end in spontaneous miscarriage.
Around 20% are stillbirths.
Inheritance:
95% of cases are de novo (new mutations, not inherited).
4–5% are familial, often due to translocation.
Maternal Age Factor:
The risk of Down Syndrome increases with maternal age. For example, at age 35, the risk is about 1 in 400, and it continues to rise with increasing maternal age.
Why Early Detection is Important
Prenatal Screening Tests: Double Marker Test, Quadruple Marker Test, and Non-Invasive Prenatal Testing (NIPT) can estimate the risk of Down Syndrome.
Prenatal Diagnostic Tests: Invasive procedures like Amniocentesis or Chorionic Villus Sampling (CVS) confirm the diagnosis.
Genetic Counseling: Helps parents understand recurrence risks and make informed decisions.
