The Church exercises great prudence with regard to such prospective marriages, as the Catechism of the Catholic Church provides in CCC 1633-37. The Church distinguishes between mixed marriages (between two Christians of different confessions) and a marriage involving Catholic and an unbaptized person (disparity of cult):
Difference of confession between the spouses does not constitute an insurmountable obstacle for marriage, when they succeed in placing in common what they have received from their respective communities, and learn from each other the way in which each lives in fidelity to Christ. But the difficulties of mixed marriages must not be underestimated. They arise from the fact that the separation of Christians has not yet been overcome. The spouses risk experiencing the tragedy of Christian disunity even in the heart of their own home. Disparity of cult can further aggravate these difficulties. Differences about faith and the very notion of marriage, but also different religious mentalities, can become sources of tension in marriage, especially as regards the education of children. The temptation to religious indifference can then arise (CCC 1634).