The aim of the present article is to give a review of the principal causes affecting embryonic mortality, and to emphasize more recent information relating to fertility losses in cattle. Based upon reviews by numerous authors, much of the loss potential offspring in cattle is concentrated in embryonic period and is more sensitive than other period in development of embryo. Moreover, it is well appreciated that the establishment and maintenance of pregnancy is a highly orchestrated process which integrates a multitude of events. Several pathogens enter the uterus by the haematogenous route or via the vagina during natural service or during insemination. Concerning the non infectious causes, chromosomal aberrations are a major cause of early embryonic mortality in animals. Heat stress is one of the environmental factors that can cause the most important decrease in reproduction performances. Some reports published which indicate an adverse effect of a high plane of nutrition or under nutrition on fertility in the bovine specie. Other important points, such as hormonal aspects, or genetic factors have been discussed in this synthesis paper.