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
- Twins
- 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
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