Recurrent miscarriage: a defect in nature's quality control?

Recent data on recurrent miscarriage (RM) is discussed in the framework of the selection failure hypothesis which states, 'Recurrent miscarriage is the result of failure of the prevention of 'poor quality' embryos implanting, allowing embryos that are destined to fail to implant and present clinically as recurrent miscarriage. Thus, recurrent miscarriage is a failure of nature's quality control.' The assumption that RM results from the maternal rejection of normal fetuses is challenged and evidence reviewed regarding the contribution of abnormal embryos and endometrial receptivity. Further research is needed to understand the mechanisms of maternal tract-embryo interaction and move towards improved management of recurrent pregnancy loss.