Question:
Answer:
Infertility is not an impediment to marriage. What you might be thinking of is the impediment of impotence. If a person is permanently incapable of consummating a marital union, he cannot marry. Consummating the marriage is a necessary component to completing the marriage. Marriages are created by being ratified (through vows) and consummated (by marital relations). A person who is permanently incapable of consummating the union is physically impeded from entering into marriage. If there is reason to hope at the time of the marriage that it can be consummated at some later point, then the couple may marry.
The Code of Canon Law states:
Antecedent and perpetual impotence to have sexual intercourse, whether on the part of the man or on that of the woman, whether absolute or relative, by its very nature invalidates marriage. If the impediment of impotence is doubtful, whether the doubt be one of law or one of fact, the marriage is not to be prevented nor, while the doubt persists, is it to be declared null. Without prejudice to the provisions of canon 1098, sterility neither forbids nor invalidates a marriage (can. 1084).