BillionToOne has gone public, marking Y Combinator’s fourth biotech to list. The company’s fetal genetic test—described by YC as one of the country’s most important—now screens about 1 in 11 babies born in the United States, giving the company broad clinical reach as it enters the public markets.
- BillionToOne is YC’s fourth publicly traded biotech.
- Its fetal genetic test is used in ~1 in 11 U.S. births.
- Public debut raises questions about reimbursement, scale and next products.
What happened
BillionToOne, a Y Combinator–backed diagnostics company, has gone public. The company built a fetal genetic test that has been widely adopted in the U.S.; according to YC, it now screens roughly one out of every eleven babies born in the country. The public listing makes BillionToOne the accelerator’s fourth biotech to enter the public markets.
Why it matters
The test’s scale gives it outsized influence on prenatal screening practice: broad use across births means more pregnancies are subject to early genetic screening and follow-up counseling, and it signals strong commercial demand for genomic diagnostics. For investors and health systems, the company’s public status will make its commercial performance, pricing and payer coverage far more visible—and could affect how quickly similar tests are adopted.
What to watch next
Key developments to monitor include reimbursement decisions by insurers and Medicaid programs, ongoing clinical uptake at hospitals and obstetrics practices, and any regulatory scrutiny tied to prenatal testing. Also watch for the company’s expansion plans—new tests, partnerships with health networks or lab operators, and quarterly public filings that will reveal revenue growth and margins as the business scales.