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What is Ideal time for doing Quadruple test? and explain in detail?
Ref. The Short Textbook of Pediatrics. Pg 600
 
Triple and Quadruple test

The triple screening measures the amounts of three substances in a pregnant woman's blood: alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and estriol (uE3)
The quad screen test is a maternal blood screening test that looks for four specific substances: AFP , hCG , Estriol, and Inhibin-A

Indications

Have a family history of birth defects
Are 35 years or older
Used possible harmful medications or drugs during pregnancy
Have diabetes and use insulin
Had a viral infection during pregnancy
Have been exposed to high levels of radiation

Timing
The triple screen test is performed between the 15th and 18th week of pregnancy