Does the Catholic Church have any process of being allowed to use birth control if it is necessary to preserve the life of the woman? (For example, suppose a woman must take certain medications to control a serious health condition and it is not allowed to take such medications during pregnancy)
It would probably a just reason to use NFP but contraception would not be permitted
2363 The spouses' union achieves the twofold end of marriage: the good of the spouses themselves and the transmission of life. These two meanings or values of marriage cannot be separated without altering the couple's spiritual life and compromising the goods of marriage and the future of the family. The conjugal love of man and woman thus stands under the twofold obligation of fidelity and fecundity.
2368 A particular aspect of this responsibility concerns the regulation of procreation. For just reasons, spouses may wish to space the births of their children. It is their duty to make certain that their desire is not motivated by selfishness but is in conformity with the generosity appropriate to responsible parenthood. Moreover, they should conform their behavior to the objective criteria of morality
The Purpose of the medication cannot be to prevent life, but to heal or prevent further illness. An example might be Chemotherapy, that weakens the body or some kind of hormone treatment (of which I don't know I'm not a doctor) that would effect the normal reproductive cycle.
Lawful Therapeutic Means
- 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.
Paul VI. (1968). Humanae Vitae. Vatican City: Libreria Editrice Vaticana.'
The idea mainly is that the Act of Sexual intercourse between a man and woman who are in the union of Sacramental marriage should always be open to the possibility of life. If the act of bonding is for purely lust of the flesh, it damages the relationship, even if it does not appear to do so on the surface. The desire for union between a Husband and Wife, is Good and beautiful, as long as that desire is is open to the relationship God intended it for. LIFE