58 As regards the evil use of matrimony, to pass over the arguments which are shameful, not infrequently others that are false and exaggerated are put forward. Holy Mother Church very well understands and clearly appreciates all that is said regarding the health of the mother and the danger to her life. And who would not grieve to think of these things? Who is not filled with the greatest admiration when he sees a mother risking her life with heroic fortitude, that she may preserve the life of the offspring which she has conceived? God alone, all bountiful and all merciful as He is, can reward her for the fulfillment of the office allotted to her by nature, and will assuredly repay her in a measure full to overflowing.
Source: Casti Connubii (Vatican.va)