The primary object of all marriage is the procreation and education of children.
As the pleasure attached to eating cannot be the purpose for which one eats, so too it is the case of marriage. The pleasure attached to the use of the sexual facility is bestowed for a definate purpose by the Creator, and that purpose is primarily the begeting of children. p.343
A word also needs to be mentioned about Natural Family Planning and periodic continance. Each method of limiting the birth of children relies on the use of the reproductive faculty only during the woman’s infertile periods, thus avoiding pregnancy. The use of the term “Natural Family Planning” has come under sharp attack from traditional Catholic writers in recent years because it implies the right of the couple to “plan” their family; whereas the Catholic norm is to let God plan ones family and to accept children when “and if” God gives them — as a blessing from him on the marital union and on society. Except for the use of NFP for fertility reasons, i.e. to aid in a legitimate way in conceiving a child(as opposed to in vitro fertilization), the** planning **aspect NFP would appear to reflect acceptance of the neo-pagan practice of “family planning” ----- albeit using “natural” as opposed to artificial means. Proponents of NFP, it would seem, are confusing a legitimate means during an emergency situation or for a “serious reason” with an *illegitimate end in the case of no family emergency or “no serious reson” and presume then to conclude that NFP is morally acceptable as a way of life.*The end or purpose of NFP–that is, “planning” one’s family–*is not acceptable *in principle, being against Natural Law and the teachings of the Church. A couple does not have the right to “plan their family,” even though the means used are those of NFP and do not violate the Church’s proscriptions against artificial birth control.
As Cardinal Ottaviani, former head of the Holy Office(Sacred Congregation for the Doctrine of the Faith), declared before the assembled bishops at Vatical Council II, "I am not pleased with the statement in the [draft] text that married couples may determine the number of children they are to have. Never has this been heard of in the Church." This is the 2,000-year tradition of the Church, suported by Sacred Scripture(cf. Genesis 38:1-10, et al.) and reiterated by the Popes in the Ordinary Teaching Magisterium of the Church (e.g. Casti Connubii------“On Marriage,” Pius XI, 1930; Address to Midwives, Pius XII, 1951; Humanae Vitae—“On Human Life,” Paul VI, 1968, No. 10)
Also, it should be noted that the Catechism of the Catholic Church(2nd Ed., 1997) does not use the term “Natural Family Planning,” Rather, it uses the term “periodic continence”(ccc, No. 2370), that is, the practice of continence, or abstinence from sexual union, during the woman’s fertile time each month.
On the other hand, periodic continence, i.e., refraining from the use of the marital act during the woman’s fertile time each month, as a “safety net” for a serious reason(cf. *Humanae Vitae, *No. 10), is completely legitimate, but only under certain very specific conditions. And they are the following:
1)That there be a serious reason to practice periodic continence.
2)That it be with the mutual consent of the marriage partners.
3)That this continence not be the near occasion of mortal sin for either party.
4)That the periodic continence last only so long as the serious reason lasts.
5)It is recommended that the situation be reviewed by one’s confessor to insure that all requisite conditions are present.