The Pap smear is a test used to detect cellular changes that, if ignored over many years, could lead to cervical cancer. Cervical cancer was once one of the leading causes of death among women. However, as Pap smears have become more common, the death rate due to cervical cancer has declined more than 70% in developed nations. Requiring women to get Pap smears once a year in order to obtain birth control pills has been an extremely effective way to encourage women to get regular Pap smears.
Very few women actually enjoy going to the gynecologist. As with any sort of preventive care, many women would choose to avoid going in for a pelvic exam if they didn't need to see the doctor for pregnancy care or to access their chosen method of birth control. In fact, scientists have long thought that one of the reasons that cervical cancer deaths remain more common in older women, other than the latency period from initial HPV infection to cancer development, is that these are women who don't need birth control pills and therefore may be less proactive about seeking out preventive care. They don't get regular Pap smears because they have a low perceived risk of sexually transmitted diseases and don't need birth control pills or pregnancy care. Therefore, without early detection, any cancer they develop is more likely to prove fatal. Lesbians may also be at high risk for cervical cancer death since they tend to be screened less often than they should for similar reasons -- no worries about unintended pregnancy, and a completely incorrect feeling that they are not at risk.
In online forums, I often see questions along the lines of "Why do I have to get a Pap smear in order to get birth control pills? I don't want a doctor poking around in my business. Only my partner should look at me down there." Questions like this clearly show why it's necessary to have the requirement. Many women find Pap smears embarrassing, and they would avoid getting them if they could get away with it and still get the other gynecological care they need. However, regular screening is essential for early detection of cervical cancer -- something for which every single sexually active woman, no matter how few people she is having sex with, is at risk. Is it paternalistic to require a Pap smear in order to get contraceptive pills? One could argue that. But it's also effective. Sometimes doctor really does know best.
Note: When a teenager goes to a doctor for birth control pills before she becomes sexually active, perhaps to regulate her period, the doctor may prescribe the pills without a pelvic exam. However, once a person is sexually active, the pelvic exam and Pap smear are almost always required.
Update 11/10: Since writing this article, I've read many women's stories of their experiences getting Pap smears, and I'm no longer in favor of using birth control pills as a way to encourage Pap screening. I still think that regular, although not yearly, screening is important; however, I think that it would be better to recruit women through education than through mechanisms that are perceived as highly coercive. Your stories have changed my mind. Thank you.
Sources: The American Cancer Society Cervical Cancer Statistics Page. http://www.cancer.org/docroot/CRI/content/CRI_2_4_1X_What_are_the_key_statistics_for_cervical_cancer_8.asp. Accessed 2/13/07. Lesbian Health. From the National Women's Health Information Center. http://www.4woman.gov/faq/Lesbian.htm. Accessed 2/13/07.
The American Cancer Society Cervical Cancer Statistics Page. http://www.cancer.org/docroot/CRI/content/CRI_2_4_1X_What_are_the_key_statistics_for_cervical_cancer_8.asp. Accessed 2/13/07.
Lesbian Health. From the National Women's Health Information Center. http://www.4woman.gov/faq/Lesbian.htm. Accessed 2/13/07.