Reasons for testing
Understanding your testing options helps you prepare for the future.
You may have many reasons for testing, including if you have:
If you are not sure whether you should have FirstScreen®, please talk with your doctor, a genetic counselor or other specialist in genetics. See “Questions to Ask Your Doctor”.
Testing for...
FirstScreen® screens for:
How the test works
Between 10-13 weeks of your pregnancy, a small amount of your blood is drawn and the levels of a protein (PAPP-A) and a hormone (hCG) are measured.
These proteins and hormones are made by your body, the developing baby and the placenta, and are found in every pregnant woman’s blood. However, when a fetus is at risk for Down syndrome or trisomy 18, the amount of these proteins may be abnormal.
The results of a special ultrasound measurement, called nuchal translucency (NT), are combined with the blood test result to yield the final screening assessment.
What's not detected
FirstScreen® does not test for open neural tube defects. A second trimester blood test called AFP or an ultrasound is required to detect open neural tube defects.
Every pregnancy has some risk (3-5%) for the kinds of birth defects that cannot be diagnosed during pregnancy, such as autism, non-specific mental retardation, some genetic diseases, and some types of physical birth defects.
Understanding results
A screening test does not provide a diagnosis; it predicts the likelihood of a problem to occur. FirstScreen® tells you if there is an increased risk of your baby having Down syndrome or trisomy 18.
FirstScreen® leads to the detection* of approximately:
- 83% of Down syndrome cases
- 80% of trisomy 18 cases
The result “screen negative” means there is a low risk of your baby having Down syndrome or trisomy 18. However, in approximately 10% of pregnancies, these birth defects will not be detected through screening.
The result “screen positive” does not necessarily mean that your baby has one of these birth defects, but does mean that there is an increased risk for them. The next step is to talk with your doctor and/or genetic counselor about your results and your diagnostic testing options.
Some factors influencing your result:
- exactly how far along you are in your pregnancy when the blood sample is taken and the ultrasound is performed
- your weight, ethnic background and age
- whether you are an insulin-dependent diabetic or take certain types of medications
- whether you have had a prior pregnancy or a close relative affected with Down syndrome or trisomy 18.
If a screening test is positive, it does not mean your baby has a birth defect. In fact, most women who have positive screening results have healthy babies.
Screening testing helps doctors to identify women who should be offered additional testing. Your doctor may recommend:
Risks of testing
FirstScreen® is a non-invasive blood test. Potential side effects from drawing blood for the test include bruising at the site or ongoing bleeding for people with bleeding disorders.
View Test Comparison Chart (PDF)
Compare testing periods, detection rates and risks for screening and diagnostic testing options.
MyTestingOptions.com will continue to add more testing options as they become available through Genzyme. Email me when more testing options are added to this website.
*Detection rate estimates for Genzyme maternal serum screening tests are based on US and international studies.
