21, 18, 13, X & Y 三體綜合症測試

What is Trisomy 21, 18, 13?

Trisomy 21(Down’s syndrome), Trisomy 18 (Edward syndrome), and Trisomy 13 (Patau syndrome) are genetic disorders associated with the presence of extra materials of chromosome 21, 18 and 13 respectively. Numerical disorders of chromosomes 21, 18 and 13 typically have various severity of mental retardation together with distinctive physical characteristics and health problems.

How common is Trisomy 21, 18, 13?

In the general population, 1:800 babies are born with Down’s syndrome. For Edward syndrome and Patau syndrome, the prevalence in newborns is 1:3,000 and 1:10,000 respectively. The likelihood that a baby will be born with the genetic disorders increases with maternal age.

What is this test for?

This test utilizes multiplex PCR analysis design for screening three common chromosomal aneuploidies-Trisomy 21(Down’s syndrome), Trisomy 18 (Edward syndrome), and Trisomy 13 (Patau syndrome) plus gender determination. DNA is extracted and purified from sample and is subjected to polymerase chain reaction (PCR) amplification. The amplified products are analyzed by gel electrophoresis using genetic analyzer.

Who should consider this test?

  • All pregnant women
  • Advanced maternal age
  • Family history of Down’s Syndrome, Edward Syndrome and Patau Syndrome
  • Maternal anxiety


3 mL amniotic fluid; or 20 mg chorionic villi
2 days