During your second trimester, you may have a quad screen, also known as a quad marker screen. The term "quad" refers to the fact that your blood is tested for four different parameters. Between the 15th and 20th weeks of pregnancy, your provider may perform a simple blood test called a quad screen.
1. Alpha Feto Protein (AFP) (null)
2. Beta HCG (null)
3. Inhibin -A (null)
4. Unconjugated Estriol(E3) (null)