Conception Claims First Early Human Eggs Grown from Stem Cells

In late June 2026, the Berkeley-based fertility startup Conception announced a notable milestone: it has generated the first early human egg cells — primary oocytes — derived entirely from stem cells. The company started with a simple blood draw, reprogrammed the blood cells into induced pluripotent stem cells (iPSCs), and guided those cells into forming miniature human ovaries containing developing early eggs.

This is not yet a mature, fertilizable egg. Conception emphasizes that the cells are still at an early developmental stage. However, the company reports that the cells display key molecular markers of primary oocytes, assemble the machinery for meiotic chromosome pairing (a critical gold-standard feature), and form fully stem-cell-derived follicles — structures in which early eggs are surrounded by supportive ovarian cells.

How the Technology Works

Conception Claims First Early Human Eggs Grown from Stem Cells The underlying approach is called in vitro gametogenesis (IVG). It begins with cellular reprogramming: ordinary somatic cells (from blood or skin) are reset to a pluripotent state using the same principles pioneered by Shinya Yamanaka, who won the Nobel Prize for discovering how to create iPSCs. These stem cells can theoretically become almost any cell type in the body.

From there, the cells are directed along the germline pathway: first toward primordial germ cells, then into early oocytes, and eventually — if the full process succeeds — into mature eggs ready for fertilization. Conception has so far completed only the early portion of this sequence, creating primary oocytes inside lab-grown mini-ovaries rather than fully mature oocytes.

The company notes that generating complete, functional follicles from stem cells alone, with cells progressing into meiosis, represents a significant technical step.

Precedent and Remaining Hurdles

The full pathway has already been demonstrated in mice. In 2016, Japanese researcher Katsuhiko Hayashi (a collaborator of Conception) turned mouse skin cells into iPSCs, produced viable eggs, fertilized them, and obtained healthy pups that later reproduced normally themselves.

Conception Claims First Early Human Eggs Grown from Stem Cells Human biology is substantially more complex. Conception itself stresses that the clinical bar is extremely high. Even if mature eggs can eventually be produced, years of safety testing, chromosomal validation, animal studies, and regulatory review would still be required before any clinical application. The company is currently focused on advancing the follicles from the primordial stage to the later antral stage, where eggs become larger and potentially usable for IVF.

Why This Matters

The most immediate potential application is treating infertility. A woman’s natural egg supply is finite and declines with age. Conventional IVF relies on hormonal stimulation to retrieve a limited number of eggs (often 10–20 per cycle), a process that carries health risks and side effects. Multiple cycles are frequently needed, each imposing further physical burden.

If IVG reaches maturity, the source of eggs would no longer be the ovary’s limited reserve. In principle, a single blood or skin sample could be expanded in the lab, generating large numbers of eggs on demand. This could dramatically expand reproductive options for people with age-related infertility, diminished ovarian reserve, or medical conditions that affect fertility.

Broader Implications: Selection at Scale

Beyond treating infertility, unlimited lab-grown eggs would remove a fundamental bottleneck in embryo selection. Companies such as Nucleus Genomics already offer polygenic screening of IVF embryos, ranking them according to predicted risks for various diseases, as well as traits related to height, cognitive scores, and other characteristics.

Conception Claims First Early Human Eggs Grown from Stem Cells Today such selection is constrained by the small number of embryos available from a typical IVF cycle. If dozens or hundreds of eggs could be produced instead of a handful, the scale of possible screening would increase substantially. Conception’s technology itself is not designed for genetic selection, but successful IVG would create the biological infrastructure that makes large-scale embryo ranking far more practical.

That prospect raises profound ethical questions about equity, the definition of “desirable” traits, the potential for new forms of reproductive inequality, and the long-term social consequences of treating human reproduction as an increasingly designable process.

A Proof of Concept, Not a Product

Conception’s announcement is best understood as a genuine scientific proof of concept rather than an imminent clinical product. Early human oocytes from stem cells have been produced; mature, safe, fertilizable eggs have not. The distance between the two remains significant.

Still, the achievement moves in vitro gametogenesis from theoretical possibility closer to an engineering challenge. If the remaining steps can be solved safely, the technology could fundamentally alter the biological constraints that have governed human reproduction for as long as our species has existed. The scientific, medical, and ethical debates that would follow are only beginning.

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