It has become almost a cliche for the Christian Right to denigrate the idea that women should be able to make their own decisions about their reproductive organs, their reproductive processes, and whether they will even reproduce or not. In effect, this takes very basic decisions about a woman's body and bodily functions away from her -- but if she is not in control of them, who is? Power and authority over women's reproductive processes are placed in the hands of men: whether it's men in their lives like husbands and fathers or predominantly male institutions like churches.
In the past, reproduction was controlled almost exclusively by social rather than chemical means; because women were generally denied basic rights and privileges accorded to men, this means that the social control of reproduction was almost entirely in the hands of men. Granting women equal civil rights -- like the right to vote, to choose whom to marry, and to divorce -- was the first step in changing this situation. Once women had the authority to make decisions about their own marriages, they had greater power to make decisions about whether and when they would have children.
The advent of chemical birth control played an even bigger role in transferring power over reproduction to women. In the past physical birth control was the responsibility of men. Today, birth control pills allow women to take personal control over their own reproductive processes. Women, acting independently, can virtually guarantee that they will not get pregnant and this frees them up to make more decisions about when and with whom they will have sex.
Most of these changes occurred or really gained force in the past half century and conservative Christianity simply has not had time to catch up -- assuming it ever will. The Christian Right relies heavily upon nostalgia for the "good old days" when women couldn't make their own, independent decisions about reproduction and sexual behavior. The corollary to this which often goes unspoken is that men would make all the decision for women.
The above image was taken from a World War II poster which is disturbing close to the theme here. It's of a woman saying "I'm proud... my husband wants me to do my part." In other words, she's proud of her husband for not just grudgingly allowing her to enter the work force, but actually wanting her to do so. Of course, she certainly lost her job and was relegated to being a homemaker as soon as the war was over.