BillionToOne Goes Public — The Startup That Made Genetic Testing Universal
Y Combinator Jared Friedman
BillionToOne, a YC-backed startup, just went public. Its prenatal genetic test is now used on 1 in 11 babies born in the US.
Based on reporting by Y Combinator, Jared Friedman — read the original for the full story.
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Eight years ago, Oguzhan Atay was still a PhD student sitting in a Stanford classroom when he decided to apply to Y Combinator with an idea that had no business succeeding on paper. Biotech startups don't move fast. They burn cash for years before anything resembles a product, let alone revenue. BillionToOne broke that pattern almost immediately, and today it's trading publicly as YC's fourth biotech company to reach that milestone.
The core insight, back in 2017, was straightforward to describe and brutally hard to execute: fetal DNA floats freely in a pregnant woman's bloodstream, so why not sequence it directly instead of relying on amniocentesis, a procedure doctors reserve for high-risk pregnancies because it's invasive. Atay and co-founder David Tsao paired biotech know-how with machine learning to filter signal from the noise in that fragmented DNA. Within six months of joining YC's Summer 2017 batch, running on little more than seed funding, they had a working test with proven accuracy. Less than two years later, it was commercially approved.
What happened next is the part that should make other founders take notice. Instead of the typical biotech grind of missed timelines and budget overruns, BillionToOne's revenue climbed steadily, beating internal targets month after month. Then Covid hit, diagnostic labs everywhere were overwhelmed, and the team pivoted their existing sequencing infrastructure to build one of the first FDA-cleared Covid tests — without slowing down growth on their main product. That's not a small feat for a company barely out of its seed stage.
The same underlying technology now stretches into cancer detection. BillionToOne launched an early liquid biopsy test in 2023, aiming to catch cancer through a routine blood draw rather than waiting for symptoms or imaging. That field is still young, but the potential payoff — early detection at massive scale — is the kind of thing that reshapes public health outcomes rather than just company valuations.
Today, the numbers tell the real story: roughly one in eleven babies born in the US gets tested using BillionToOne's technology. That's not viral growth for an app. That's a genetic test becoming default clinical practice in under a decade, built by two PhD students who convinced a fund with zero biotech track record to bet on them anyway.
My take — AI-written commentary, not fact-checked reporting
This is the rare biotech story that didn't need a decade and a billion dollars to prove the model works, and it's a useful counterexample to the narrative that AI and machine learning are mostly hype layered on top of consumer apps. Genetic testing quietly becoming routine for pregnant women in America matters more than another chatbot launch, even if it gets a fraction of the headlines. The liquid biopsy push for cancer is the part worth watching closely — if that scales the way prenatal testing did, this company's IPO will look like the least interesting thing about it.
Read more about this at: Y Combinator