Multiple Marker Screening
Other names for these tests: Triple Marker; Triple Screen; Double Screen; Quadruple Screen, Maternal Serum AFP Screen
The Multiple Marker Screening checks for two to four of the following: AFP, HCG, Estriol (E3) and Dimeric inhibin A. Estriol is a byproduct of estrogen metabolism and is affected by the health of baby and the placenta. Dimeric inhibin A is made in the ovaries. This test is generally done between 15-20 weeks gestation which is 17-22 weeks pregnancy.
The Triple Screen is a blood test measuring the Alfa-Feto Protein (AFP), Human Chorionic Gonadatropin (HCG) and estriol levels. It is more accurate at predicting Down Syndrome than the AFP alone, but it can miss 20-30% of cases of Down Syndrome in women over 35, and 40% in women under 35.
Out of 1000 tests performed, 25-50 will report increased levels and 2 will actually have a neural tube defect. There is a high rate of false positives, but 90% of neural tube defects are detected with this screen. False positives are possible due to:
Pregnancy not dated properly
A different "open" birth defect
A placental wall defect or bleeding
Weight, race and presence of diabetes all effect the levels.
If your test comes back high your choices will be to:
Repeat the test and compare the results
Use ultrasound to examine the baby. Ultrasound can see some neural tube defects, check age and check for twins
Use amniocentesis to determine health of baby
If your test comes back low your choices will be to:
Use ultrasound to examine the baby. Ultrasound can help to check age and undetected miscarriage.
Test for maternal diabetes
Amniocentesis to determine health of baby