Twenty years of epidemiology in fertility regulation.

ABSTRACT

PIP: Epidemiological research serves to continue surveillance of fertility regulation agents once phase 3 clinical trials have been completed and the contraceptives have been marketed. Epidemiologic research conducted during the past 20 years has had a major impact on family planning program policies and clarified many concerns about contraceptive side effects that emerged in the early 1970s. Central has been the reassessment of the risk of malignant neoplasms associated with use of hormonal contraception. Data from large-scale studies such as the Cancer and Steroid Hormone Study in the US and the World Health Organization Collaborative Study involving 9 developing and 2 developed countries suggest that combined oral contraceptives (OCs) decrease the risk of ovarian and endometrial cancer, especially in long-term users. Although there is emerging evidence that OC use exceeding 5 years is associated with a modest increase in cervical cancer risk, the causality of the association is questionable given the probable influence of confounding factors such as sexually transmitted diseases. Moreover, epidemiologic studies launched in the 1980s confirmed that the previously noted association between OCs and cardiovascular diseases has been reduced as a result of lower doses of ethinyl estradiol and revised prescribing practices. Other foci of epidemiologic investigations have included possible side effects associated with natural family planning, the impact of modern IUDs on pelvic inflammatory disease and ectopic pregnancy risks, and the association between vasectomy and testicular and prostate cancer. Given the observational nature of epidemiologic research and the potential for bias, findings from several studies addressing the same research question with different methodological approaches are generally assessed.