Alphafetoprotein (afp) Testing
Alpha-fetoprotein (afp) screening (also called quadruple marker testing or the "quad screen") can help identify fetal spinal cord or cranial defects (also known as neural tube defects or NTD's), chromosomal abnormalities as well as other possible birth defects.
It is a blood test (on your blood) taken at about 16-17 weeks of pregnancy. Four components in your blood are measured. This test is usually offered to women under the age of 35. If every patient under age 35 took the afp test, about 2/3 of babies with Down’s syndrome would be identified, but the other 1/3 would be missed.
The AFP program is administered by the state of California, and test results take about 8-10 days.
A normal test means the following. First, it is extremely unlikely that your baby will have an open spinal or cranial defect (i.e. spina bifida). Second, it is also unlikely that Down's syndrome or any other chromosomal abnormality is present. An abnormal test result does not mean that your baby will definitely have a defect. An abnormal test only suggests that further study is needed.
If there is any abnormality with your alpha-fetoprotein blood test, you will be referred to a specific testing center, authorized for afp follow-up by the State of California.