Largest Prospective Study in General-Risk Pregnancies Strengthens Evidence for cfDNA Fetal Risk Assessment as a Primary Screen for Recessive Conditions

Study of more than 2,200 pregnant carriers demonstrates strong clinical performance in the intended-use, general-risk population, with outcomes available for more than 98% of eligible cfDNA results MENLO PARK, Calif. , Aug. 18, 2026 /PRNewswire/ -- BillionToOne, Inc. (Nasdaq: BLLN ), a next-generation molecular diagnostics company with a mission to create powerful and accurate tests that are accessible to all, today announced publication of A Prospective, Multi-Site Study of Performance of Cell-Free DNA Testing for Recessive Conditions in a Large, General-Risk Pregnancy Population in The Green Journal . This is the first prospective NIPT study conducted in an intended-use screening population with near-complete pregnancy outcome ascertainment, providing important new evidence supporting routine use of cfDNA fetal risk assessment in general-risk pregnancies. Conducted across nine U.S. institutions, the prospective study evaluated 2,212 pregnant carriers in which partner carrier status was unknown at the time of testing. Unlike studies enriched with known high-risk couples or pregnancies with other indications of increased fetal risk, this design reflects how cfDNA fetal risk assessment is used as a primary screen in routine prenatal care. Investigators assessed these carriers with cfDNA fetal risk results for cystic fibrosis, spinal muscular atrophy, and alpha- and beta-hemoglobinopathies, collecting outcomes for 98.6% of pregnancies completing care at participating sites. Traditional carrier screening depends on partner testing to determine fetal risk, but partner follow-up is often incomplete, delayed, or unavailable due to logistical, financial, and access barriers 1 . Unity Fetal Risk Screen demonstrated 94.4% sensitivity, confirming that this approach identifies more affected pregnancies than traditional carrier screening alone, which classifies fewer than 50% of affected pregnancies as high-risk, mainly due to incomplete partner screening. This advantage holds even in the ideal scenario in which every partner completes testing: carrier screening detects approximately 90% of spinal muscular atrophy carriers, 95% of alpha-thalassemia cases, and up to 99% of cystic fibrosis carriers, and the tested partner may not always be the biological father. Unity Fetal Risk Screen overcomes both limitations by assessing fetal risk directly rather than inferring it from parental genotypes. In addition to excellent sensitivity, the assay demonstrated 99.5% specificity and >99.9% negative predictive value. Unity Fetal Risk Screen provides a personalized, quantitative fetal risk as high as 9-in-10 — compared to the maximum 1-in-4 risk offered by traditional screening when both partners are confirmed carriers — and as low as 1 in 10,000, giving patients added reassurance. "Multi-center studies with this level of outcome completeness are rare in prenatal screening," said Eliza McElwee, MD, Assistant Professor College of Medicine Department Obstetrics Gynecology at Medical University of South Carolina. "These results provide clinicians with a much stronger evidence base for incorporating cfDNA fetal risk assessment into routine carrier screening, with data that are directly relevant to everyday clinical practice." The study also demonstrated consistent performance across a racially and ethnically diverse population, supporting equitable access to prenatal genetic screening without the need for partner testing. Researchers point to the growing urgency of early detection, as new therapies show that earlier diagnosis can meaningfully change outcomes for affected children. "This publication shows that carrier screening with cfDNA fetal risk assessment performs reliably in the general-risk population, not just in a research setting," said Haywood Brown, MD, Chief Medical Officer, Prenatal at BillionToOne. "For patients, that means a high-risk pregnancy is far less likely to be missed simply because a partner sample was never collected." Unity Fetal Risk Screen is part of BillionToOne's Unity Complete ® prenatal screening portfolio, combining carrier screening, cfDNA-based fetal risk assessment, and aneuploidy screening to deliver prenatal genetic information from a single maternal blood draw via the company's proprietary Quantitative Counting Template™ (QCT™) technology. The publication follows BillionToOne's recent announcement that it is expanding its fetal risk screen portfolio to include a new 130-gene panel, reflecting the company's continued investment in advancing comprehensive prenatal screening and fetal risk assessment. About BillionToOne Headquartered in Menlo Park, California, BillionToOne is a next-generation molecular diagnostics company with a mission to create powerful and accurate tests that are accessible to all. The company's proprietary single-molecule next-generation sequencing (smNGS) platform is the only multiplex technology that can detect and precisely quantify genetic targets at the physical limit of d