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The idea of studying in detail the various diseases that might affect fecundity was prompted by reading Reynolds Farleys "Growth of the Black Population." Farleys health hypothesis focuses primarily on changes in venereal disease (VD) prevalence and was put forword to explain the decline and subsequent risk in US black fertility during the 1st 1/2 of the 20th century. This monograph was designed to examine closely all aspects--medical pathological and epidemiological--of all diseases that might alter human reproductive potential. The examination of pathophysiology of the diseases reveals ways in which diseases can affect fecundity. Absolute coital inability is an infrequent sequela of most of the diseases. However a few diseases are accompanied by impotence complete or partial obstruction of the vaginal opening or genital deformities that make coitus impossible. Male and female conceptive failure are discussed as is pregnancy loss. Disease may lower fertility rates by Davis-Burke intermediate variables other than subfecundity. The importance of selected diseases in historical developing and developed societies is discussed. Pitfalls in population subfecundity research can be divided into 5 general categories: 1) limitations of existing data on the prevalence of diseases and/or subfecundity; 2) effects of the social setting on disease and subfecundity prevalence; 3) persistent myths about certain disease; 4) the unreliability of indirect evidence; and 5) the variability of response to a disease by population.

A populations fecundity is the average fecundity of its individual members. The relative contribution of the male and female disorders to subfecundity is difficult to pinpoint. It is estimated that male subfecundity accounts in whole or in part for 20% to 60% of the subfecundity in various populations. In the US the concensus is that men contribute to subfecundity in 30% to 40% of the cases and the women in 60% to 70%. The actual fertility of almost all populations ranges from only 1 to 8 children/women; with about 4 being the world average in 1982. In addition to subfecundity a societys fertility level is determined by various forms of birth control and by the fact that much of an individuals reproductive period is spent without regular coital activity. 1 task of fertility studies is to determine the relative impact of subfecundity birth control and mate exposure factors that are characterized as intermediate variables. Subfecundity has depressed fertility since the human race began. It is also an important fertility determinant in contemporary developing societies. The prevalence of subfecundity in these societies is given especially Africa and Asia. Improvement in health during modernization might lead to a reduction of subfecundity and to a subsequent rise in fertility. Health manpower by occupation rate/100000 population and density is given in charts. Subfecundity factors are still demographically important in developed societies. The prevalence of subfecundity for these societies is given especially for the US and its impact on fertility discussed. Life expectancy at birth is an important measure of a populations health. Effect of timing on fertility is discussed as is the ability of subfecundity to influence fertility behaviorally through the other intermediate variables. These are: 1) phase of fertility and 2) subfecundity-birth control-mate exposure categories. A research project identified 5 categories of factors which influence population subfecundity: 1 psychopathology; 2) disease; 3) nutritional deficiencies; 4) environmental factors; and 5) genetic factors.