This node will develop over time, but for now this will give the clear points as to what the Roman Catholic Church teaches and an interesting way of viewing it.

First, conjugal activity is exclusively for husband and wife. Secondly, God's created design is that the unitive and procreative dimensions of conjugal activity are intimately related. Genuine marital love-giving is intimately related to life-giving. Thus, sexual pleasure, not sinful in and of itself, is expressive of genuine marital love, and cannot mean anything else. Hence, it can not be excluded from it, and any activity that would exclude the life-giving aspects of the intimate act, are inherently evil.

Another way of putting this is to repeat what Professor Janet Smith of the University of Dallas once said to her students:

First, Professor Smith told her students to make a private list of all the people that they wanted to have sex with. And then, she told them to make a list of all the people that they wanted to have babies with. The request for the second list made her point and helps one to understand the point of the Roman Catholic Church.