Contraception, Unintended Pregnancies, and Sexually Transmitted Diseases: Why Isn't a Simple Solution Possible?

Abstract

Epidemiologists have shown us the importance of using a population-level approach to public health problems. Geoffrey Rose for example quantified the relationship between exposure to a causal agent and the associated risk of developing a disease. He also described the several forms that this relationship could take including a threshold effect a linear construct a U-shaped relationship and an inverted U-shaped curve. Based on this quantification Rose showed that prevention strategies that focus on high-risk individuals may benefit those individuals but will likely have little impact on the total disease burden in the population because more cases of disease occur among the many who are at low risk than among the few who are at high risk. Applying these concepts to the relationship of contraceptive choices and the prevention of unplanned pregnancies and sexually transmitted diseases (STDs) allows the description of a natural history of the sexual and reproductive events in a population of females which reveals that the risk of unplanned pregnancies and STDs exists for nearly the entire reproductive period. Unfortunately no currently-available contraceptive provides good protection against both outcomes and a wide variation has been found in the level of contraceptive effectiveness against these outcomes in different populations. A further complication is that the best available method to date the male condom is not female-controlled (and the female condom is not widely accepted). Therefore to move toward a social norm of the lowest risk for any sexual exposure we need a spectrum of imperfect yet cumulatively effective strategies made possible by a wide array of contraceptives.