A double marker test is a prenatal screening test that assesses the risk of chromosomal abnormalities in a developing fetus. It involves measuring levels of two specific substances, beta-hCG (human chorionic gonadotropin) and PAPP-A (pregnancy-associated plasma protein A), in the mothers blood.Abnormal levels of these markers can indicate an increased risk of conditions like Down syndrome or trisomy 18.While not diagnostic, this test helps identify pregnancies with a higher likelihood of chromosomal issues, allowing for further diagnostic testing if necessary.