Ideal time for doing Quadruple test?
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
15-18 weeks
12-14 weeks
10-12 weeks
8-10 weeks