Pregnancy-associated plasma protein A (
PAPP-A) is a key regulator of
insulin-like growth factor bioavailability essential for normal fetal development. In maternal blood, this
protein increases with gestational age and then rapidly decreases after delivery. It is routinely used for
Down syndrome screening in the first trimester of pregnancy, and its decrease compared to a normal pregnancy indicates an increased risk for both chromosomal anomalies and adverse pregnancy outcomes. It belongs to a group of
biomarkers that predict later
preeclampsia development, primarily early onset
preeclampsia; however, it should be combined with a Doppler ultrasonography of the uterine artery (pulsatile index) and other biochemical and maternal factors to achieve a higher detection rate with an acceptable false positivity rate. Some studies have demonstrated an even more pronounced decrease of
PAPP-A in the early second trimester of pregnancy in women who subsequently develop
preeclampsia compared with women who do not develop
preeclampsia. Conversely, during the last trimester of pregnancy, its concentration increases even more in patients with
preeclampsia than in patients without. It is also detectable at very low levels in nonpregnant individuals, and a higher concentration indicates an adverse effect in patients with
acute coronary syndromes or stable atherosclerotic disease and in patients with
end-stage renal disease who are being treated with
hemodialysis.