Some research suggests that the use of oral contraceptives (birth control pills) may increase a woman's risk of developing cervical cancer. The connection between human papillomavirus (HPV) infection and cervical cancer, however, is clearer. HPV infection is known to play a causative role in the development of cervical cancer. To date, studies of oral contraceptive use and cervical cancer risk have not adequately examined the combined role of HPV infection and oral contraceptives. Now, a study recently published in
suggests that long-term use of oral contraceptives may greatly increase the risk of cervical cancer among women with HPV infection.
An international group of researchers analyzed data from 10 studies of oral contraceptive use and cervical cancer conducted between 1985 and 1997 by the International Agency for Research on Cancer (IARC). The IARC studies were conducted in Spain, Colombia, Paraguay, Peru, Brazil, Morocco, Thailand, and the Philippines. All of the studies were case-control studies, meaning that researchers enrolled women who had cervical cancer (cases) and women who did not (controls) and asked about their lifetime use of oral contraceptives. The women were also tested for HPV infection. Cases and controls were matched in terms of age, and women who had other cancers or disorders associated with cervical cancer were excluded from the control group.
For this recent analysis, the researchers studied only the women who tested positive for HPV infection—1676 cases and 255 controls. This was an attempt to examine whether HPV and oral contraceptives somehow work together to increase the risk of cervical cancer. The researchers compared the number of cervical cancer cases among women who took oral contraceptives with the number of cases among women who did not.
Among the women with HPV infection, those who took oral contraceptives for fewer than 5 years were not at higher risk of cervical cancer than women who never took oral contraceptives. However, women who took oral contraceptives for 5 to 9 years were about 3 times more likely to develop cervical cancer than never-users. And women who took oral contraceptives for 10 years or more were 4 times as likely to develop cervical cancer than never-users. Interestingly, among women who stopped taking oral contraceptives six years or more before the study, the risk of cervical cancer was close to that of never-users.
Of note was that the analysis showed that oral contraceptive use was not associated with a higher risk of HPV infection.
In calculating these statistics, researchers accounted for other factors that might affect cervical cancer risk, such as age, education, number of Pap smears, number of births, number of sexual partners, and age at first sexual intercourse.
Although these results are interesting, there are limitations to this study. First, it is a meta-analysis, meaning that the researchers collected data from several studies and analyzed it together in an attempt to derive an overall estimate of risk. Although the IARC studies had similar designs, meta-analyses lack a certain degree of precision, though they do help to synthesize data from many similar studies. In addition, researchers in these studies relied on the participants to recall their lifetime use of oral contraceptives accurately, which may not always be the case. Finally, the questionnaires used in these studies did not collect information about the type of oral contraceptive used—for example, estrogen only, estrogen/progestin combination, progestin only. Therefore, it remains unclear whether all oral contraceptives carry the same level of risk. In addition, some of the women may have used injectable rather than oral hormonal contraceptives.
Should you be taking oral contraceptives if you have HPV infection? Probably not. Although this study suggests that oral contraceptives may be safe for short-term use in women with HPV, these findings suggest that long-term use increases the risk of cervical cancer. These findings confirm the findings of other studies that oral contraceptive use may increase risk for cervical cancer, but they indicate that the increased risk may be a result of the combination of HPV infection and oral contraceptive use. If you have HPV infection and want to practice contraception, talk to your health care provider about which forms are safest for you.
Moreno V, et al. Effect of oral contraceptives on risk of cervical cancer in women with human papillomavirus infection: the IARC multicentric case-control study.
. Published online March 27, 2002.
Skegg DCG. Oral contraceptives, parity, and cervical cancer.
. Published online March 27, 2002.
Last reviewed Mar 29, 2002
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