Why are miRNA levels elevated during pregnancy?

Pregnancy causes profound systemic changes in miRNA expression throughout the body. The placenta is an exceptionally rich source of extracellular miRNA — it actively secretes miRNA-containing exosomes into maternal circulation, elevating the overall miRNA burden in blood and urine. Specifically, placenta-associated miRNAs and broadly expressed oncomiRs like miR-21 can rise substantially during normal, healthy pregnancy. Because these elevated miRNA levels would overlap with the cancer threshold, a pregnant woman's result could be falsely elevated even in the absence of cancer. This is why pregnancy is a clear contraindication for OncuraKit — the test cannot reliably distinguish cancer-associated miRNA overexpression from pregnancy-associated miRNA elevation.