BillionToOne Goes Public — The Startup That Made Genetic Testing Universal

Going public means BillionToOne has become a publicly traded company rather than remaining privately held. Its shares can be bought and sold by public-market investors. The milestone makes it YC's fourth publicly traded biotech company, but the article emphasizes a larger achievement: its prenatal test has become important in U.S. healthcare.

The company began when Oguzhan and David were PhD students and applied to YC in 2017. Their idea was to read fetal DNA fragments in a mother's blood. Within six months, using modest funding, they had built the test and shown accuracy on test samples. They launched an approved commercial test in less than two years.

Public trading does not change what the test detects. It marks a new corporate stage after rapid, predictable revenue growth and expansion into liquid biopsy cancer testing. BillionToOne is now working toward blood tests that could detect cancer early, when it is most treatable, potentially saving millions of lives at scale.

BillionToOne's prenatal genetic test is used for 1 in 11 babies born in the United States. That is a striking level of reach for a company whose founders were still PhD students when they applied to YC in 2017. The article presents the test as one of the most important genetic tests in the country.

The test examines fetal DNA fragments that naturally circulate in the mother's blood. This approach allows genetic abnormalities to be assessed without beginning with an invasive procedure. Before BillionToOne, most such abnormalities could be detected only through amniocentesis, which was generally used in high-risk pregnancies.

The scale reflects both technical success and commercial execution. BillionToOne built and validated the test within six months, launched an approved commercial version in less than two years, and then grew revenue predictably. The company is also developing liquid biopsy technology for cancer detection, using the same core approach.

The test analyzes fragments of fetal DNA that naturally exist in a mother's blood. Its goal is to identify genetic abnormalities in the fetus. The article does not name particular abnormalities; it describes the test as a way to detect fetal genetic problems from free-floating DNA rather than through an invasive procedure.

The core mechanism combines DNA sequencing with machine learning. Sequencing reads the genetic information carried by many small DNA fragments. Those fragments create noisy data because fetal DNA is free-floating in the mother's blood. Machine learning helps interpret that data and make sense of the signal well enough to identify abnormalities.

This matters because the method can assess fetal genetics through a blood sample. BillionToOne developed the actual test and demonstrated its accuracy on test samples within six months of applying to YC. Today, the test is used for 1 in 11 babies born in the United States.

The blood-based test was a major alternative because it avoids starting with amniocentesis. Amniocentesis is an invasive procedure, and the article says it was used only in high-risk pregnancies. A test based on fetal DNA already circulating in maternal blood offers a less invasive route to genetic information.

BillionToOne's founders believed prenatal testing could work by sequencing these free-floating fetal DNA fragments. The challenge was that the fragments produce noisy sequencing data. Their solution fused biotech expertise with machine learning, allowing the company to interpret the fragments and identify genetic abnormalities. They built the test and proved its accuracy on test samples within six months.

The approach also supported broader adoption. BillionToOne launched an approved commercial test in less than two years and now tests 1 in 11 babies born in the United States. The article presents this widespread use as evidence that the alternative moved from a founding idea to a major healthcare product.

DNA sequencing provides the raw information. It reads genetic material from the fetal DNA fragments naturally present in the mother's blood. Because the fragments are free-floating and mixed into a blood sample, the resulting data is noisy rather than a clean, direct genetic sample.

Machine learning helps make sense of that noise. It can analyze patterns across the sequencing results and help identify the fetal signal relevant to genetic abnormalities. The article describes this combination as a fusion of biotech expertise and machine learning. It does not describe the specific algorithms, but it makes clear that computation is required to interpret the fragmented data.

BillionToOne showed the approach could work in practice. Within six months of applying to YC, the founders had developed the test and proven its accuracy on test samples. The method then became an approved commercial product, reaching 1 in 11 babies born in the United States.

When a genetic test becomes commercially approved, it moves from research into practical healthcare use. Providers can order and use it as an available clinical product, while patients can access testing through the healthcare system. In this case, the test offers fetal genetic information from a blood sample rather than beginning with invasive amniocentesis.

BillionToOne demonstrates the change clearly. Before the company, most genetic abnormalities could be detected only through amniocentesis, which was used in high-risk pregnancies. BillionToOne sequenced fetal DNA fragments in maternal blood and used machine learning to interpret the noisy results. It launched an approved commercial test in less than two years.

The result is broad adoption: 1 in 11 babies born in the United States are tested with it. Commercial availability also supports predictable growth and further development. BillionToOne launched an early cancer liquid biopsy commercially in 2023, extending the technology beyond prenatal testing.

A liquid biopsy uses a blood sample instead of a tissue procedure to look for cancer-related genetic material. BillionToOne's core technology detects free-floating DNA, the same basic capability used in its prenatal test. The article says this approach can also detect cancer through blood, although liquid biopsy technology is still in its infancy.

The mechanism is to sequence free-floating DNA fragments and use the company's technical systems to interpret the signal. In prenatal testing, the signal comes from fetal DNA in the mother's blood. For liquid biopsy, the target is DNA associated with cancer. The article identifies the shared foundation as detecting tiny amounts of free-floating DNA.

BillionToOne launched an early version of its cancer test commercially in 2023. Its longer-term goal is a blood test people could take regularly to detect cancer early, when it is most treatable. At scale, the article says such testing could save millions of lives.