PAPP-A (Pregnancy Associated Para Protein-A)

PAPP-A (pregnancy-associated plasma protein A) is a placental protein measured in maternal blood during the first trimester. It is a metalloproteinase that increases insulin-like growth factor availability by cleaving IGF-binding proteins. Low PAPP-A levels are associated with higher risk of chromosomal abnormalities (e.g., Down syndrome), miscarriage, preeclampsia, and fetal growth restriction, so it’s used in combined pregnancy screening.

To convert PAPP‑A to MoM, divide the patient’s measured PAPP‑A concentration by the gestational‑age–specific median value from your lab or population reference. Use the same assay units. Apply recommended correction factors (maternal weight, ethnicity, smoking, diabetes, IVF and assay method) to the resulting MoM if required. Report the final MoM with the reference medians and adjustments used.

PAPP‑A (pregnancy‑associated plasma protein A) rises in early pregnancy and is typically reported as multiples of the median (MoM) during first‑trimester screening (about 9–14 weeks). Normal first‑trimester values are roughly 0.4–2.5 MoM; values below ≈0.4 MoM are considered low and may prompt further evaluation. Absolute mIU/L reference ranges vary by lab and gestational age.

High PAPP-A in pregnancy is less often problematic than low levels. It can reflect inaccurate dating, multiple pregnancy, or placental overgrowth (e.g., molar/trophoblastic disease). High PAPP-A usually doesn’t indicate chromosomal anomalies but prompts reassessment of gestational age and follow-up scans. Management typically involves confirming dates and continued monitoring of fetal growth and maternal health.

PAPP‑A (pregnancy‑associated plasma protein A) by itself is not an immediate diagnosis but a screening marker. Low first‑trimester PAPP‑A can be linked to increased risk of chromosomal abnormalities and placental problems (growth restriction, preeclampsia, preterm birth). It often prompts further testing—detailed ultrasound, noninvasive prenatal testing or diagnostic tests—and closer monitoring. Many pregnancies with low PAPP‑A proceed normally, so discuss next steps with your clinician.

PAPP‑A is typically low in pregnancies affected by Down syndrome. In first‑trimester screening, reduced maternal serum PAPP‑A, together with increased free β‑hCG and increased nuchal translucency, raises the calculated risk for trisomy 21. Low PAPP‑A alone is not diagnostic but contributes to combined screening algorithms; abnormal results prompt offer of diagnostic testing such as CVS or amniocentesis.