. The Double Test is a prenatal screening test typically performed during the first trimester of pregnancy, usually between 11 and 14 weeks.
. It involves measuring two key biomarkers in the mother's blood: Pregnancy-Associated Plasma Protein A (PAPP-A) and free β-hCG. These markers, when combined with the mother's age and other factors, help assess the risk of chromosomal abnormalities such as Down syndrome (Trisomy 21) and Edwards syndrome (Trisomy 18).
. The test does not diagnose these conditions but provides risk assessment, identifying pregnancies that may require further diagnostic testing like amniocentesis or chorionic villus sampling (CVS). It is often used in conjunction with other screening tests, such as the nuchal translucency (NT) ultrasound and crown-rump length (CRL) for a more comprehensive risk evaluation.