In most dairy systems, the ability to establish pregnancy following insemination is the primary definition of fertility. Highly fertile cows establish pregnancy sooner after calving and require fewer inseminations. Pregnancy is a logical endpoint for defining the fertility phenotype because it is typically recorded on farm and can be verified by using calving dates. Pregnancy is established through a series of individual events that occur in sequence. In postpartum cows, for example, estrous cycles are re-established, estrus is expressed and detected, sperm are deposited in the reproductive tract and capacitate, ovulation occurs and is followed by fertilization, and the corpus luteum forms and produces sufficient progesterone to maintain pregnancy. The oviduct supports early cleavage and the uterus establishes a receptive environment for the developing pregnancy. Each individual event is theoretically heritable and these events collectively contribute to the phenotype of pregnancy after insemination. Genetic selection as it is practiced today does not target individual mechanisms leading to pregnancy because they are difficult to phenotype reliably on a large number of cows. Dairy systems differ with respect to reproductive management applied to cows. In some systems, cows are inseminated after detected estrus with minimal intervention. In these systems, the establishment of pregnancy early postpartum effectively captures the summation of the individual events leading to pregnancy. More intensive systems that use hormonal treatments (PGF_2α, GnRH, etc.) followed by timed AI do not invalidate the current phenotypes but the individual components that contribute to the phenotype may be more or less important to the establishment of pregnancy. Uterine release of PGF_2α and the establishment of adequate circulating estradiol to cause an endogenous GnRH surge and estrus expression, for example, are not necessary to establish pregnancy when timed AI is used. Selecting cows for a functional reproductive system comprised of individual components involved in the establishment of pregnancy may ensure uniform performance of future cows across a variety of reproductive management systems.