Not many in the current debate realize that the Bible contains a book that celebrates non-reproductive sex and features substances used by ancient women for birth control. The book, Song of Songs (also known as Song of Solomon or Canticles), is a dialogue of love and sexual passion associated with King Solomon. It depicts a woman and a man (it's not clear that the man is Solomon) who desire each other and see each other in secret. Yet, it is not clear that they are married, children are not mentioned as a goal of their love, and their dialogue is laced with mentions of materials that we know were used in ancient Egypt, Mesopotamia and/or Greece to prevent pregnancy. A biblically based morality linked with the Song of Songs need not oppose, but could promote use of birth control as part of caring, monogamous sexual relationships, whether within marriage or not.
To be sure, many have associated the biblical Song of Songs with marriage (it's frequently used for Christian pre-marriage counseling), and there are indications that the lovers it depicts wish that they were married. The man calls his love "my bride" (e.g. 4:8, 9), and she sings that "I am my love's and he desires me" (7:11). Nevertheless, toward the end of the book the female lover still cannot openly express her affection for him (8:1). Overall, the book positively depicts a couple pursuing a love that is not approved by society. It begins with the woman wishing that the man would "kiss me with the kisses of his mouth," and soon she is inviting him to her bed of spices. The lovers do not live together, but instead must meet outdoors (e.g. 1:17) or in a parent's bedroom (3:4; 8:2), and there is no clear view yet of starting a family. In the process, the lovers mention a number of spices (e.g. pomegranates, honey, myrrh, spikenard) that Athalya Brenner points out in her book "The Intercourse of Knowledge: On Gendering Desire and 'Sexuality' in the Hebrew Bible" (Leiden: Brill, 1996, 72-89) were used by ancient women to prevent pregnancy.
Perhaps most importantly, the book does not suggest anywhere that their sexual relationship is wrong. Their love leads to suffering at points, especially for the woman (5:2-6). Nevertheless, Song of Songs celebrates their unsanctioned sexual passion. At the same time the book repeatedly urges caution in engaging in such love, especially through a repeated urging not to "awaken or arouse love until love is ready" (2:7; 3:5; 8:4). Later, the woman sings of how "Love is strong as death, jealousy as harsh as Sheol" (8:6). Thus love is a powerful, sometimes dangerous thing. Such power should not be played with. It is not to be taken lightly. Nevertheless, as one of my students at Union Theological Seminary, Elizabeth Bukey, pointed out, "it's easier to list what the Song does not teach. It does not say you've got to be married. It doesn't say men should dominate women and it doesn't get worked up about which particular sexual acts are OK." Instead, the book stresses that one must take care in deciding when "to awaken or arouse love." Perhaps one aspect of that care would be in following the example of the woman of the Song of Songs and taking precautions, when needed, not to have unplanned children. Say, using effective birth control.
Of course, we now know much more than ancient women did about how to prevent birth. Moreover, studies also suggest that birth control lowers medical costs for women by preventing expensive unwanted pregnancies, and unwanted pregnancies also can add to broad societal costs which all taxpayers pay. Therefore, one might say that the issue now is not protecting the religious freedom of religious employers who want to impose costs of birth control on students and employees. Instead, it is an issue of protecting the religious rights of those who have no problem with birth control (some even seeing the Song of Songs as a religious endorsement of that position). People who affirm the use of birth control (including out of religious conviction) should not have to pay the extra medical and societal expenses incurred when women are excluded from good access to birth control by religious authorities opposed to it.
In sum, one might get the impression from recent debates that Christianity, or the Bible more specifically, has only one position on sexuality. Yet, closer study of texts like the Song of Songs reveals that things are much more complicated.