PAPPA (Pregnancy-Associated Plasma Protein A): PAPPA is a protease that regulates the availability of insulin-like growth factors (IGFs) by cleaving their binding proteins. It plays a vital role in foetal development and is used as a biomarker in prenatal screening for aneuploidies. Abnormal levels of PAPPA are linked to adverse pregnancy outcomes, including pre-eclampsia and intrauterine growth restriction.