• Often the child is unwanted; worse, it is feared; how could readiness for duty still exist in such a condition? Here is your apostolate [the Pope is speaking directly to the midwives] must be practiced in an effective and effective manner: first of all, negatively, rejecting any immoral cooperation; therefore also positively, turning your delicate care to dispelling preconceptions, the various apprehensions or pusillanimous pretexts, to push away, as much as possible, even external obstacles, which can make accepting motherhood painful. If we do not resort to your advice and your help to facilitate the procreation of new life, to protect it and guide it towards its full development, you can certainly lend your cooperation; but in how many other cases are you resorted to to prevent the procreation and preservation of this life, without any regard to the precepts of the moral order? Comply with such requests, it would be a lowering of your knowledge and ability, making you complicit in an immoral action; it would be a perversion of your apostolate. This requires calm, but categorical "no", who does not allow the law of God and the dictates of conscience to be transgressed. Therefore your profession forces you to have a clear knowledge of that divine law, in order to enforce it, without staying on this side, nor go beyond its precepts.
• Our Predecessor Pius XI of happy memory in his Encyclical Casti Connubii of 31 December 1930 solemnly proclaimed again the fundamental law of the marital act and relations: that any attempt by the spouses in the fulfillment of the marital act or in the development of its natural consequences, attack with the aim of depriving it of the strength inherent in it and preventing the procreation of a new life, it is immoral; and that no "indication" or necessity can change an intrinsically immoral action into a moral and lawful act (cfr. Ap Act. Sedis vol 22, p. 559 and following.).
• This prescription is in full force today as yesterday, and it will be so tomorrow and always, because it is not a simple precept of human right, but the expression of a natural and divine law. (…) So oppose it, as far as it is from you, in your apostolate to these perverse tendencies [the Pope refers to contraception and sterilization] and deny them your cooperation. (…)
• [In the following paragraphs the Pontiff condemns the use of marriage exclusively in times of natural sterility; therefore he urges those spouses who find themselves in "very delicate cases for their health" to practice "heroic abstinence". Indeed: «God does not force the impossible. But God forces spouses to abstinence if their union cannot be accomplished according to the norms of nature. Therefore in these cases abstinence is possible. We have the doctrine of the Council of Trent as confirmation of this argument, which, in the chapter on observance, necessary and possible, of the Commandments, sign, referring to a passage from Saint Augustine: “God does not command impossible things, but while he commands, he warns, and do what you can, and to ask what you cannot, and help so that you can”» (Conc. You want. Sess. 6 cap. II Denzinger n. 804 – S. August. On nature and grace chap. 43 n. 50 Migne P. L. vol. 44 col. 271)]. (…)
• The individual and society, the people and the state, the Church itself, they depend for their existence, in the order established by God, from a fruitful marriage.
Dal Speech of His Holiness Pius XII to midwives
Source: https://www.sursumcorda.cloud/articoli/centro-studi-vincenzo-ludovico-gotti/2130-papa-pio-xii-sull-uso-immorale-del-matrimonio-e-sulla-contraccezione.html