Technical Abstract: Mechanisms involved in pregnancy establishment and maintenance in cattle are complex. Approximately 95% of matings, regardless of whether they are by artificial insemination or natural service, result in fertilization. However, rarely do 70% of these matings result in a pregnancy that is maintained through gestation. The majority of pregnancy losses occur from fertilization until day 27 of gestation during the period defined as early embryonic mortality. Adequate progesterone concentrations during the preceding estrous cycle and during early pregnancy, along with proper nutrition are important for an ideal maternal environment. Inadequate energy, excess protein (especially rumen degradable protein), and both thermal and handling stress are able to cause early embryonic mortality by decreasing progesterone, increasing uterine prostaglandin release, decreasing uttering pH, and increasing blood urea nitrogen and ammonia. Understanding the role that managers can assume to control some of these variables should result in greater pregnancy establishment and maintenance as well as an economic return for their efforts.