The relationship between squamous carcinoma of the cervix and oral contraceptive use has been examined in a substantial number of epidemiological studies. On balance there is reasonably convincing evidence that prolonged oral contraceptive use slightly increases the risk of the disease, but some doubt remains as to whether or not confounding factors have been controlled adequately in the studies reporting positive findings. The data are too few at present for any reasoned comment to be made about the possible relationship between oral contraceptives and adenocarcinoma of the cervix.
PIP: A literature review of the risk of developing squamous carcinoma of the cervix related to taking oral contraceptives, from 3 types of epidemiological studies, case- control, cohort and transit time studies, concludes that there is suggestive evidence for a slight increased risk with length of use. Of 14 large case-control studies, 10 found risk higher than 1. The 2 largest and carefully designed found risks of 1.5 and 1.8 Cohort studies show rising risks with length of use, e.g, 0.9 to 2.9 per 1000 woman-yrs in women using pills for 2 to 8 years in California, and 0.21 to 1.01 per 1000 woman yrs for no use to 10 yr in the U.K. Few good transit-time studies are available: no increased risk from pill use is evident from these studies. There are fundamental difficulties and omissions in all these studies, such as assessing the bias due to sexual behavior, the biological effect of age when pill use began, and the contribution of sexual behavior of the male partner. No studies to date have examined the issue of the type of pill used.