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