Work on models of human reproductive process comprised of both discrete and continuous models postulating both homogeneity and heterogeneity of the population. A historical review of the models reveals that the models differ only in-treatment of time as Discrete or Continuous. In many of the models, the probability of conception is held constant and further assumption is made in regard to all conceptions which lead to live births and which are associated with a fixed non-susceptible period covering the gestation period and the period of post-partum amenorrhea. However, introducing further the notion of time when conception is recorded has also evolved new type of more flexible and realistic probability models. ukryj opis