Family planning and fecundity.

Abstract A computerized probability model of family-building, FERMOD, is described and then utilized in an investigation of relations between family planning and fecundity as applying to white couples of the contemporary United States. Models of this type that formulate reproductive performance as a stochastic process permit one to explore relations that are not directly observable and in this manner to secure at least partial answers to questions not subject to investigation by survey research alone. Two main questions are addressed concerning the dependence of family planning success upon fecundity: (1) How quickly does spacing control deteriorate when natural fecundability is taken at progressively lower values or when the risk of pregnancy wastage is set at progressively higher values? (2) What is the distribution of unsought births among couples of average fecundity when they practise contraception with specified effectiveness and have stipulated spacing and family size goals?