Conservative evangelical objections to contraception, emergency contraception, and even abortion can often be traced at least in part to their objections to "irresponsible" sexual activity. Attempts to avoid pregnancy are thus attempts to avoid the consequences of one's "irresponsible" choices. Since avoiding the consequences of irresponsible choices is itself irresponsible as well as something which makes such choices easier, it follows that people should be forced to bear those consequences. When it comes to sexual activity, this includes women accepting pregnancy.
Many will deny that they perceive pregnancy as a "punishment" or something which women must "suffer," but a close examination of common language and arguments reveals that this attitude often lurks beneath the surface. It may be an unconscious attitude, so those who deny it may be sincere and really not realize what they are doing. Hopefully, if they reflect upon it enough, they will recognize what it going on and make some changes.
One of the most important developments of the "Sexual Revolution" was to transform people's expectations about sexuality and sexual behavior. Whereas before sexual intimacy was expected to be limited to marriage (though it often wasn't in practice), afterwards people began to expect such intimacy even in non-marital relationships. Sex has become an expression of physical, emotional, and psychological intimacy in a variety of relationships, not just marriage. Being able to avoid some of the consequences of sex - especially pregnancy - has been a key factor making this development possible.
Making it harder for people to avoid pregnancy would make it harder for people to engage in sexual activity outside the boundaries of what the Christian Right deems morally licit. Some actually do want more women to get pregnant; most, however, seem to hope that the fear of pregnancy will induce more women to just say "no" to sex at all. In this way, pregnancy is definitely being treated like punishment not unlike fines or jail are a punishment designed to alter people's behavior.
The above image was originally a World War II poster designed to encourage people to buy more war bonds. The headline said "I Gave a Man!" She has sacrificed far more than those who are only being asked to spend at least 10% of their earnings on war bonds to help fund the war effort.