Fertility rates globally decrease. This is in parts caused by exposure to omnipresent environmental pollutants such as microplastics, flame retardants, and plastic softeners. Pregnancy starts with the implantation of a developmentally competent embryo into the receptive endometrium. Novel (stem) cell-based models can be used to study these early stages of pregnancy. Curiously, species employing embryonic diapause as reproductive strategy have high reproductive success rates. During diapause, the pre-implantation embryo pauses reversibly to ensure favourable conditions for the developing offspring. Using cell-based models, my lab will use embryonic diapause as a model to understand the factors that contribute to developmental competence of the embryo and how the endometrium becomes receptive. Eventually, we will investigate the mechanisms though which environmental pollutants contribute to the globally declining fertility.