BillionToOne is a molecular diagnostics company that runs genetic tests from blood samples, serving two markets: prenatal care and oncology. In prenatal, BillionToOne's flagship product is UNITY, a suite of non-invasive prenatal tests (NIPTs) that analyze cell-free fetal DNA from a single maternal blood draw. UNITY's core differentiator is its ability to assess fetal risk for recessive single-gene conditions — like sickle cell disease and cystic fibrosis — without requiring a paternal blood sample, which traditional carrier screening requires. UNITY also screens for chromosomal abnormalities, fetal RhD status, and fetal antigens relevant to hemolytic disease of the fetus and newborn. In oncology, BillionToOne offers two liquid biopsy tests under the Northstar brand: Northstar Select guides therapy selection by detecting mutations in circulating tumor DNA, and Northstar Response monitors treatment response using methylation signals. Both are sold directly to clinicians via a direct sales force. BillionToOne receives blood samples, performs proprietary molecular analysis, and bills insurers or patients per test. Revenue grows through test volume and average selling price (ASP). ASPs are currently well below established CMS reimbursement rates, as a meaningful share of tests are still reimbursed out-of-network or not reimbursed at all — expanding in-network coverage is the primary ASP growth lever. The company's tests are built on its proprietary single-molecule next-generation sequencing platform, which enables precise quantification of scarce DNA fragments, including fetal or tumor DNA present at very low concentrations in a blood sample.