September 30, 2022 Human ‘Blastoids’ Offer Medical Hope But Also Deep Ethical Challenges A team of bioethicists and a cellular biologist in Japan discuss the ethical challenges in human blastoid research. © Kanon Tanaka Research performed on human blastoids, a research model of an early embryo built out of stem cells, may allow scientists to understand better what causes birth defects and lost pregnancies, and so prevent them. But such research is also ethically fraught, warn bioethicists, due to differing beliefs on whether the blastoid possesses sentience or has the potential to do so. The study of blastoids, a research model of an early embryo derived from stem cells rather than from a father’s sperm or a mother’s egg, offers great hope for researchers investigating why pregnancies are lost at an early stage, what causes birth defects, and other topics related to early human development. Their use potentially avoids the challenges of scarcity and potential ethical problems of using