Maternal Serum Triple Screen
The maternal serum triple screen is a general term for a blood test known by several brand names such as AFP-3, Triscreen, Downscreen Plus, Trisomy Profile, AFP Plus, etc. This is a screening test used in pregnancy to help identify pregnancies at increased risk for certain birth defects. Knowledge of these birth defects may change the pregnancy management for you and your health care provider. There are two main types of birth defects for which the test screens: Down syndrome and neural tube defects (spina bifida and anencephaly). These are usually not inherited, and occur unexpectedly.
The test is drawn between 15 and 20 weeks of pregnancy. Correct gestational age is extremely important in the interpretation of the test. The laboratory measures the levels of three chemicals in the mother's blood which are made either by the fetus or the placenta during pregnancy. These levels, along with information about the mother and the pregnancy, are used to calculate the risk for Down syndrome and spina bifida.
It is important to understand that the blood test is a screening test, not a diagnostic test. It cannot tell if the abnormality is present or not. Research has shown that in approximately 80-90% of pregnancies where a neural tube defect is present, the blood test will be abnormal and the patient will be offered an opportunity to consider further diagnostic testing. This means that the test can detect the majority of cases of Down syndrome and spina bifida but it cannot detect all of them. It is important to remember that most women who receive an abnormal screening result go on to have normal, healthy babies. However, a genetic consultation/evaluation is recommended to review your individual blood test results and to discuss the risk which has been identified in your pregnancy. The types of further diagnostic testing which are available and applicable to your situation will be discussed, including their risks, benefits, and limitations. Such further diagnostic options may include high-resolution ultrasound, amniocentesis, or both, depending on your situation. It will be your decision whether or not to proceed with further diagnostic testing. The genetic counselor will also review your family medical history and pregnancy history in order to determine whether other risk factors are present, and will help to clarify your concerns and answer your questions.
View this site to see other tests (how they are performed, what they test and what is done afterwards):