label: Embryo developmental arrest
label_lc: embryo developmental arrest
description: A failure of an embryo to progress through the early stages of preimplantation development (typically from fertilization, i.e., 1-cell zygote, to blastocyst on day 5-6), and is used clinically when embryos fail to reach transferable stages in assisted reproductive technologies (ARTs) such in vitro fertilization (IVF). Arrested embryo development is characterized by downregulation of metabolic activity and cessation of cell division. In order for an embryo to be characterized as non-viable, i.e., arrested, it should present with a lack of cleaving activity and fail to show a sign of mitotic cellular division for at least 24 hours. One can observe failure of a zygote to cleave, cleavage stage arrest either on day 2 or day 3 when the embryo is expected to be between the 2 and 8-cell stage, failure to compact to morula, or failure to form a blastocyst.