Frustrated fertility: a population paradox.

This Bulletin examines the causes of subfecundity -- the diminished ability to reproduce -- and its effect today and in the past on the fertility, or actual reproductive performance, of individuals and, hence, populations. By definition, all real populations are subfecund since all experience some degree of involuntary biological factors affecting coitus, conception, or the ability to carry a conceptus to live birth which reduces their fecundity below the estimated biological population maximum of 15 children per woman. Affecting both men and women, these factors fall into 5 categories: genetic factors such as blood group incompatibilities and inherited sickle cell anemia or diabetes; psychopathology, including psychic stress and behavioral disorders (e.g., drug and alcohol abuse); infectious diseases such as gonorrhea, malaria, tuberculosis, and postabortion infection; malnutrrition, including the chronic undernutrition of the 3rd World and the overnutrition of developed societies; and hazards posed by increasing amounts of radiation and toxic chemicals in the environment. Reducing subfecundity requires improved living conditions, avoidance of or protection from known hazards, and adoption of medical advances which now can help 40 to 60% of subfecund couples. But even in the U.S. fertility would certainly rise among the 15% of couples now estimated to be involuntarily childless and the 10% who have fewer children than they want, and among disadvantaged groups, and teenagers.