Pope Pius 12, declared in 1951 that it is possible to be exempt from the normal obligation of parenthood for a long time and even for the whole duration of married life, if there are serious reasons, such as those often mentioned in the so-called medical, eugenic, economic and social ``indications.'' This means that such factors as the health of the parents, particularly the mother, their ability to provide their children with the necessities of life, the degree of population density of a country and the shortage of housing facilities may legitimately be taken into consideration in determining the number of offspring.

These are substantially the same factors considered by non-Catholics in family planning. The laws of many states permit birth control only for medical reasons. The Roman Catholic Church, however, sanctions a much more liberal policy on family planning.

Catholics, Protestants and Jews are in agreement over the objectives of family planning, but disagree over the methods to be used. The Roman Catholic Church sanctions only abstention or the rhythm method, also known as the use of the infertile or safe period. The Church considers this to be the method provided by nature and its divine Author: It involves no frustration of nature's laws, but simply an intelligent and disciplined use of them. With the exception of the Roman Catholic and the Orthodox Catholic Churches, most churches make no moral distinction between rhythm and mechanical or chemical contraceptives, allowing the couple free choice.