Reasons for testing
Understanding your testing options helps you prepare for the future.
Your reasons for testing may include:
- concerns regarding Down syndrome and trisomy 18
- concerns regarding open neural tube defects in pregnancy, such as spina bifida
- a family history of Down syndrome, trisomy 18, or open neural tube defects
If you are not sure whether you should have Afp4®, please talk with your doctor, a genetic counselor or other specialist in genetics. See “Questions to Ask Your Doctor”.
Testing for...
Afp4® screens for:
How the test works
Between approximately 15 and 21 weeks of your pregnancy (the optimal time is between 16 and 18 weeks), a small amount of your blood is drawn and certain proteins and hormones are measured. These proteins and hormones are made by your body, the developing baby and the placenta during pregnancy, and are found in every pregnant woman’s blood. However, when a fetus is at risk for Down syndrome, trisomy 18 or an open neural tube defect, the amount of these proteins may be abnormal.
What's not detected
Afp4® does not screen for chromosome abnormalities or birth defects other than those mentioned above.
Understanding results
A screening test does not provide a diagnosis; it predicts the likelihood of a problem to occur. Afp4® tells you if there is an increased risk of your baby having Down syndrome, trisomy 18 or an open neural tube defect.
Afp4® leads to the detection* of approximately:
- 81% of Down syndrome cases
- 80% of trisomy 18 cases
- 80% of open neural tube defects
The result “screen negative” means there is a low risk of your baby having Down syndrome, trisomy 18 or an open neural tube defect. However, in approximately 20% 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
- 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, trisomy 18, or an open neural tube defect
Screening helps doctors to identify women who should be offered additional testing. Your doctor may recommend:
- a more detailed ultrasound examination (which can often identify an open neural tube defect)
- diagnostic testing, such as amniocentesis for Down syndrome, trisomy 18 and open neural tube defects
