The presence of high levels of aneuploidy in oocytes and early embryos and their fate is of considerable scientific and clinical importance. The Origins of Aneuploidy Research Consortium (OARC) was established to promote interdisciplinary communication and collaborative research into this topic. Under the umbrella of OARC, a series of papers has now been published in this Special Issue of Prenatal Diagnosis. Recent studies have transformed the view that aneuploidy is usually attributable to meiotic non-disjunction. The molecular basis for the association between meiotic error and maternal age is becoming understood. The clinical significance of mitotic instability in the earliest cells divisions of the embryo is also becoming clearer. An error in the segregation of one or more whole chromosomes from a parent does not invariably result in a non-viable pregnancy or an abnormal outcome. Epidemiologic data allows an assessment of in utero viability, the effect of maternal age, and secondary factors that may affect aneuploidy prevalence. We advocate careful use of nomenclature and revision of educational materials to more accurately explain the complex and often nuanced mechanisms. OARC plans to hold additional workshops, promote additional publications and offer educational resources.
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