Tetra Test = Quad Test = AFP Test = Down Syndrome Screening
What does it test for?
Maternal blood tests show whether the baby is at higher-than-average risk for certain birth defects of the brain and spine (called neural tube defects) and Down syndrome as well as a few other chromosomal birth defects.
When is it done?
It's usually performed at about 16 weeks, but anytime between 16-20 weeks is acceptable.
How is it performed?
A simple blood sample is taken from the mother.
What does it measure?
Through research, medical science has discovered that the measurement of four hormones produced in significant quantities during pregnancy can be measured in the blood stream of the mother. These four hormones should fall within a range as calculated based on large number of normal pregnancies. If any one of the four levels falls above or below the normal expected range based on gestational age, maternal weight, and race, it is used to calculate the rate at which the specific birth defect is likely to occur.
What if the results are abnormal?
Nine of ten women receive normal results and breathe a sigh of relief. But there is a high rate o false positive which means that on average 10 percent of women will end up with an abnormal result. Don't panic -- chances are the baby is fine. Because this is a screening test, many more babies are shown to be at risk than actually have problems. In fact, for every 100 women with abnormal results, only 2 or 3 have a baby with birth defects. In most cases, abnormal test results occur because your baby is either a few weeks older or younger than originally thought, which throws off the reading. So if you have an abnormal result, the first step your healthcare provider will take is to give you an ultrasound to ensure accurate dating and if not accurate recalculate your baby's age. The ultrasound will also show if you're carrying twins -- another common cause of an abnormal blood test. If your baby's age or the fact that you're carrying multiples explains your result, you probably won't need any further tests. This ultrasound is done by a maternal fetal specialist or perinatologist and reviews the anatomy of your baby as well. By looking at specific anatomical images, the ultrasound also helps to determine if all looks normal or if there is a true problem in which case further testing such as an amniocentesis would be recommended.