What is a quad screen?
A quad screen is a blood test that measures four things in your blood. These are called alpha-fetoprotein, human chorionic gonadotropin, inhibin A, and unconjugated estriol. The results of the blood test can help your doctor determine if your baby may be at higher risk for certain birth defects, such as Down syndrome and neural tube defects.
What is a penta screen?
A penta screen measures a fifth substance called hyperglycosylated human chorionic gonadotropin.
Why is it called a "screen"?
These test results can only show that there may be a problem, but they cannot prove that there definitely is one. An abnormal test result doesn't necessarily mean that your baby has a birth defect. Most often, the blood test results are abnormal because the baby is younger or older than your doctor initially thought. Some birth defects will not be detected by this test. Remember, this test does not screen for all birth defects.
When should the test be done?
Quad and penta screens are most accurate when done between the 16th and 18th weeks of pregnancy.
What happens if the test results of the screen are abnormal?
Your doctor will probably want you to have an ultrasound to check on the age of the baby and look for problems in the baby's brain, spinal cord, kidneys, and heart. Your doctor may want you to talk to a genetic counselor (an expert who can explain the results), get some additional testing, and see a doctor who specializes in high-risk pregnancy.
Maternal Serum Triple Analyte Screening in Pregnancy by Graves JC, Miller KE (American Family Physician March 01, 2002, http://www.aafp.org/afp/2002/0301/p915.html)
Written by familydoctor.org editorial staff