Pregnancy-Associated Plasma Protein-A (PAPP-A) is a protein produced by the placenta during pregnancy. Its levels naturally increase in the mother’s bloodstream as pregnancy progresses. Measuring PAPP-A is a standard component of prenatal care, routinely assessed during the first trimester as part of a comprehensive screening process.
The Role of PAPP-A in Pregnancy Screening
PAPP-A levels provide insight into placental function and fetal development. This measurement is part of the “first-trimester screen,” conducted between 11 and 14 weeks of gestation. PAPP-A levels are not interpreted alone; they are integrated with other markers for a more comprehensive risk assessment.
These markers include human chorionic gonadotropin (hCG), a hormone produced during pregnancy, and nuchal translucency (NT). Nuchal translucency is an ultrasound measurement of the fluid-filled space at the back of the fetal neck.
The combined results of PAPP-A, hCG, and NT are entered into a computer algorithm. This algorithm calculates an individualized risk score for certain chromosomal conditions, such as Down syndrome. This is a screening test, designed to identify pregnancies with increased risk, rather than a diagnostic test.
Interpreting Low PAPP-A Levels
Low PAPP-A levels are often reported as a Multiple of the Median (MoM), which compares an individual’s level to the average for that gestational age. A PAPP-A MoM below 0.4 is considered low and can suggest an increased risk for chromosomal conditions. These conditions include Trisomy 21 (Down syndrome) and Trisomy 18 (Edwards syndrome).
Low PAPP-A levels can also be associated with placenta-related complications later in pregnancy, even if fetal chromosomes are typical. These complications include preeclampsia (high blood pressure) and intrauterine growth restriction (IUGR), where the baby does not grow as expected. A low PAPP-A level might also indicate an increased risk of preterm birth (delivery before 37 weeks).
Many individuals with low PAPP-A levels have healthy pregnancies and babies. Low PAPP-A primarily indicates a need for closer observation, rather than a definitive problem.
Understanding High PAPP-A Levels
Elevated PAPP-A levels are not considered a clinical concern during pregnancy. Unlike low levels, which prompt further investigation, high PAPP-A is not associated with adverse pregnancy outcomes. Elevated PAPP-A levels do not require additional follow-up or monitoring. This distinction helps reassure individuals with higher PAPP-A levels, as it is a less common finding that rarely necessitates intervention.
Next Steps and Monitoring
Upon receiving a PAPP-A result that indicates a low level, the next step involves a detailed discussion with a healthcare provider or a genetic counselor. This consultation helps to place the results in proper context, considering other factors in the pregnancy. Further testing options are available to provide more definitive information about the baby’s chromosomal status.
One common option is non-invasive prenatal testing (NIPT), a blood test that screens for chromosomal conditions with higher sensitivity than the first-trimester screen. For a definitive diagnosis, chorionic villus sampling (CVS) or amniocentesis can be performed.
CVS involves taking a small sample of placental tissue, usually between 10 and 13 weeks, while amniocentesis involves sampling amniotic fluid, typically after 15 weeks.
If diagnostic tests confirm normal chromosomes, the focus may then shift to monitoring for placenta-related risks identified by the low PAPP-A. This could involve more frequent ultrasound scans to track fetal growth and development, along with regular blood pressure checks for the pregnant individual.