Contraception Within Marriage

The Church teaches that the intention of contraception is contrary to the divine plan.

However, there are cases where a medical treatment may have two effects: one is the treatment of a medical condition and the other is contraceptive. In such a situation, so long as the contraceptive effect is not willed and the contraceptive effect is not the means of treatment, the medical treatment is moral.

Humanae Vitae:

15. On the other hand, the Church does not consider at all illicit the use of those therapeutic means necessary to cure bodily diseases, even if a foreseeable impediment to procreation should result there from—provided such impediment is not directly intended for any motive whatsoever.