Pregnant or not? Alpha-fetoprotein (AFP) is used during pregnancy as part of the "Quad Screen". This is a test that includes AFP and three other blood chemicals to screen for Trisomy 18, Trisomy 21 and Neural Tube defects. If the quad screen is abnormal, a referral to see a perinatologist for a detailed ultrasound and additional testing is in order. AFP can also be tested as part of a cancer work-up.