The PAPP-A test, which stands for Pregnancy Associated Plasma Protein A, is a blood test used during the first trimester of pregnancy as part of a combined screening test. It's not a test to confirm pregnancy itself.
Purpose of the PAPP-A Test
The PAPP-A test is used to assess the risk of certain chromosomal abnormalities in the fetus, primarily Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and Patau syndrome (Trisomy 13).
How the PAPP-A Test Works
The test measures the level of PAPP-A, a protein produced by the placenta. Abnormal levels of PAPP-A, combined with other factors, can indicate an increased risk of chromosomal abnormalities. These other factors include:
- Nuchal Translucency (NT) Measurement: An ultrasound measures the fluid-filled space at the back of the baby's neck. Increased NT can indicate a higher risk.
- Maternal Age: The risk of chromosomal abnormalities increases with maternal age.
- Gestational Age: The timing of the test is crucial for accurate results.
The results of the PAPP-A test, the NT measurement, and maternal age are combined using a computer algorithm to calculate a risk assessment for chromosomal abnormalities.
Important Considerations
- Screening Test, Not Diagnostic: The PAPP-A test is a screening test, meaning it identifies pregnancies at higher risk for chromosomal abnormalities. It does not provide a definitive diagnosis.
- Follow-Up Testing: If the screening test indicates an increased risk, further diagnostic testing, such as chorionic villus sampling (CVS) or amniocentesis, is offered to confirm the diagnosis.
- Timing: The PAPP-A test is typically performed between 10 and 13 weeks of pregnancy.
In summary, the PAPP-A test helps assess the risk of certain chromosomal abnormalities during the first trimester and is used in conjunction with other factors to determine the need for further diagnostic testing. It does not confirm pregnancy itself.
