Overview
Pregnancy-associated plasma protein A, commonly known as PAPP-A, is a large glycoprotein produced by placental trophoblasts and released into maternal serum during pregnancy. It is most important in first-trimester screening and plays a key role in regulating insulin-like growth factor bioavailability, which is essential for normal placental development and fetal growth. PAPP-A levels normally increase with advancing gestational age and fall rapidly after delivery. It is one of the two markers used in the dual marker test, along with free beta hCG, for early risk assessment of chromosomal abnormalities and pregnancy-related complications.
Symptoms
PAPP-A itself does not produce direct symptoms, but abnormal levels are associated with clinical outcomes affecting the mother and fetus. Low PAPP-A levels in early pregnancy are linked with poor fetal growth, pregnancy-induced hypertension, preeclampsia, preterm delivery, intrauterine growth restriction, and stillbirth. Very low levels are frequently associated with adverse pregnancy outcomes. Abnormal PAPP-A levels may also indicate an increased risk of chromosomal abnormalities such as Down syndrome, trisomy 18, and trisomy 13.
Causes
Low PAPP-A levels are caused by abnormal placentation and impaired trophoblast invasion in early pregnancy. Reduced proteolytic activity of PAPP-A affects the insulin-like growth factor system, leading to impaired placental development and fetal growth restriction. Low levels are strongly associated with chromosomal abnormalities and pregnancy-related hypertensive disorders. Elevated PAPP-A levels may occur in normal pregnancies with healthy placental function, while increased levels outside pregnancy are associated with atherosclerosis, plaque instability, and acute coronary syndromes.
Risk Factors
Risk factors for abnormal PAPP-A levels include chromosomal abnormalities, placental dysfunction, and a history of adverse pregnancy outcomes. Pregnant women with a history of preeclampsia, intrauterine growth restriction, or stillbirth are at higher risk of low PAPP-A levels. Advanced maternal age, underlying vascular disease, and metabolic disorders may also influence PAPP-A levels. Inaccurate gestational dating or a lack of proper ultrasound correlation can affect interpretation.
Prevention
Prevention focuses on early screening and close monitoring rather than direct prevention of abnormal PAPP-A levels. Performing the dual marker test within the recommended gestational window allows early identification of high-risk pregnancies. Combining PAPP-A results with free beta hCG levels and nuchal translucency measurement improves risk assessment accuracy. Pregnancies identified as high risk require increased surveillance, timely intervention, and individualized prenatal care to reduce complications and improve maternal and fetal outcomes.
