What are the rates for double marker test?

Answer 1

There are no specific quantitative values for the separate parts of the First Trimester screen. (Double Marker Test). This is a screening too, used to assess risk factors.

The test is most accurate between the 16th week and the 18th week and the correct fetal age is mandatory for accurate testing.

The blood screen measures two pregnancy related hormones: hCG and PAPP-A.

The ultrasound evaluation measures nuchal translucency (fluid beneath the skin behind baby's neck).

You will be told whether your results are "normal or abnormal", and you will be given a risk level by your genetic counselor/OB. The counselor will give you your risk factor for chromosomal abnormalities based on the test results (for example 1/250, 1/1300).

A positive test means that you have a 1/100 to 1/300 chance of experiencing one of the abnormalities. Using a maternal blood screening test with an ultrasound evaluation of the fetus to identify risk for specific chromosomal abnormalities, including Down's Syndrome Trisomy-21 and Trisomy-18.

When the test results come back in the typical range, this result reduces the woman's risk of having a child with Down syndrome.

If the woman is 25, this decreases her risk from 1/1100 to 1/4400.

If the woman is 35 years old, this decreases her risk from 1/250 to 1/1000.

If the woman is 45, it decreases her risk from 1/20 to 1/80.

85 out of 100 babies affected by the abnormalities the screen tests for will be identified.

5% of the tests will be false positive.