Researchers from Stanford and international partners have built lab-grown human uterine lining that supports embryo attachment, enabling direct study of the earliest implantation events. Three studies in Cell describe models tested with donated embryos and stem-cell–derived blastoids, with all experiments halted before 14 days. The systems may help improve IVF success but also reignite ethical debates about extended laboratory growth and the limits of ectogenesis.
Lab-Grown Human Uterine Lining Lets Scientists Observe Embryo Implantation — Raises IVF Hope and Ethical Questions
A doula holds a replica of an embryo in the womb. | stock.adobe.com
Researchers at Stanford, working with teams in the U.K., Spain and China, have engineered lab-grown human endometrium (the uterine lining) that can support embryo attachment — enabling the first detailed observations of the initial stages of implantation. Three studies describing these systems were published together in the journal Cell, and the groups say their models are the most faithful reconstructions yet of very early pregnancy events.
What the teams built
Stanford investigators collaborated with researchers at Cambridge, the Babraham Institute (U.K.) and a laboratory in Spain to recreate the tissue environment an embryo encounters when it implants. In related work, teams in China, working with scientists at UT Southwestern (Texas), rebuilt portions of the endometrium inside small silicone chambers using cells and tissue from human uterine linings.
How experiments were run
Into these laboratory models the scientists placed both donated IVF embryos (from infertility treatments) and stem-cell–derived structures called blastoids. Blastoids mimic an early embryo stage and can be generated without sperm or eggs. The Beijing group reported testing roughly 50 IVF embryos alongside about 1,000 blastoids as they refined their system.
Teams observed attachment and the earliest cellular and molecular interactions under the microscope. In all cases the experiments were halted before a 14-day threshold in keeping with prevailing legal and ethical guidelines.
Why this matters
Greater visibility into implantation could help improve in vitro fertilization (IVF): studies suggest around 75% of transferred embryos fail to implant. By revealing the first "cross-talk" between embryo and maternal tissue, the models may point to new ways to increase implantation success and reduce failed transfers.
A graphical abstract from a study published on Dec. 23, 2025, of the 3D post-implantation co-culture of human embryo and endometrium. | Jinzhu Song et al., Cell Press
Technical next steps
Investigators say they are working to make the systems more physiologically realistic by adding blood vessels, immune cells, micro-pumps and perfused blood supplies so the models better mimic in vivo conditions.
Ethical concerns and limits
Although researchers emphasize that current systems are not functional artificial wombs, bioethicists warn of a potential slippery slope toward prolonged laboratory growth of human embryos. A Wake Forest bioethicist said efforts to extend embryo culture could become “very troubling” if they enable longer-term development outside the body. Other commentators argued that the work raises deeper questions about the moral status of embryos and appropriate legal limits.
Jun Wu (UT Southwestern): “For the first time, we observed the entire sequence of human implantation.”
Balance and context
Scientists involved emphasize that these are early-stage research tools intended to illuminate a poorly understood and clinically important process, not to create babies outside a womb. Several leaders in the field stress the work remains far from a functioning artificial womb and that ethical and legal guardrails — such as the 14-day limit widely observed in many jurisdictions — continue to guide experiments.
Bottom line
Lab-grown uterine models now let scientists watch the earliest moments of implantation in unprecedented detail. The advances could help improve IVF outcomes, but they also intensify urgent ethical discussions about how far laboratory systems should be allowed to replicate or support human development.
