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Down syndrome can be diagnosed through a combination of screening tests and diagnostic tests.The quad screen in the second trimester measures four pregnancy-associated substances: alpha fetoprotein, estriol, HCG, and inhibin A. Diagnostic Tests During Pregnancy: Chorionic Villus Sampling (CVS): Performed between 10 and 13 weeks of pregnancy, CVS involves taking cells from the placenta to analyze fetal chromosomes.Here's how it works: Screening Tests During Pregnancy: First Trimester Combined Test: This two-step test includes a blood test to measure levels of pregnancy-associated plasma protein-A (PAPP-A) and the pregnancy hormone human chorionic gonadotropin (HCG).

Down syndrome can be diagnosed through a combination of screening tests and diagnostic tests. Here’s how it works:
Screening Tests During Pregnancy:
First Trimester Combined Test: This two-step test includes a blood test to measure levels of pregnancy-associated plasma protein-A (PAPP-A) and the pregnancy hormone human chorionic gonadotropin (HCG). An ultrasound measures nuchal translucency (a specific area on the back of the baby’s neck). These results estimate the risk of carrying a baby with Down syndrome.
Integrated Screening Test: Combining results from both the first and second trimesters, this test includes blood tests for PAPP-A and an ultrasound to measure nuchal translucency. The quad screen in the second trimester measures four pregnancy-associated substances: alpha fetoprotein, estriol, HCG, and inhibin A.
Diagnostic Tests During Pregnancy:
Chorionic Villus Sampling (CVS): Performed between 10 and 13 weeks of pregnancy, CVS involves taking cells from the placenta to analyze fetal chromosomes. It confirms or rules out Down syndrome.
If screening test results are positive or worrisome, further diagnostic testing may be recommended.
Postnatal Diagnosis:
After birth, Down syndrome can be confirmed through genetic tests that examine the appearance and number of chromosomes in the baby.