ABSTRACT
In the jargon of demographers fecundity, the physiological ability to reproduce, is distinguished from fertility, the realization of that potential, the actual birth performance as measured by the number of offspring. Puberty marks the age at which, under the stimulus of increased flows of several hormones, secondary sex characteristics develop and, later, the reproductive organs become operative. Demographers use a term to designate all the factors that affect fertility—physiological, cultural, and other, omitting only birth control and the bearing of a child. Some analysts believe that prehistoric man used various primitive means of contraception. Data on the deaths of mothers, fetuses, newborns, and infants all show that the risks rise on either side of an optimum age range, but authorities differ on what that range is. Multiple births are relatively rare in the human species except when they are stimulated by hormones administered as a therapy for infertility.
