Stem cell-based embryo models as a tool for reproductive biology.

ART has transformed clinical practice but still faces modest success rates, poorly defined implantation conditions, and persistent gaps in understanding early human development. At the same time, research in human reproductive biology remains strikingly underfunded relative to its medical and social impact. Over the last decade, advances in human pluripotent stem cell (PSC) biology have generated a suite of technologies that can recapitulate early stages of human development from blastocyst formation to early gastrulation in vitro. Here, we review how such models can be harnessed to interrogate lineage specification, embryo-endometrium crosstalk, the origins of aneuploidy and implantation failure, and the developmental basis of placental and yolk sac disorders, with a focus on primates. We argue that integrating stem cell-derived embryo models into reproductive research agendas offers a tractable experimental framework to improve ART outcomes and address major unmet needs in human reproductive health.