Combination oral contraceptives, containing orally active estrogen and progestin sex steroids, occupy a central role in the continuing effort: to provide safe, reliable, effective, and reversible contraception to a large segment of reproductive-aged women. Oral contraceptives are an effective means of contraception with a method failure rate of 0.1% to 0.2% and a user failure rate of 3% to 6%.<sup>12 Killick S.R. Patient education and understanding: A critical review Adv Contracept 1992 ;  8 (S1) : 57

Haga clic aquí para ir a la sección de Referencias</sup> A reason for this disparity in rates is the need for daily pill use from days 1 through 21 to achieve maximal efficacy. Compliance and acceptability issues can lead to suboptimal use and a subsequent increased risk for unplanned pregnancy.

Another factor associated with suboptimal oral contraceptive use and increased risk of unplanned pregnancy is the commonly held belief that routine oral contraceptive use is associated with numerous health risks.<sup>19 Peipert J.F., Gutmann J. Oral contraceptive risk assessment: A survey of 247 educated women Obstet Gynecol 1993 ;  82 : 112

Haga clic aquí para ir a la sección de Referencias</sup> Cardiovascular and cancer risks are commonly reported by women as concerns when they consider using oral contraceptives.<sup>19 Peipert J.F., Gutmann J. Oral contraceptive risk assessment: A survey of 247 educated women Obstet Gynecol 1993 ;  82 : 112

Haga clic aquí para ir a la sección de Referencias</sup> Such fears and misperceptions can lead some women to use other contraceptives that are either not as effective as oral contraceptives or that are characterized by a side-effect profile that results in poor acceptance and use. In either situation, women are more prone to contraceptive misuse or disuse and thus exposed to a higher risk for unplanned pregnancy.

Despite widespread concerns regarding the risks of routine oral contraceptive use, safety issues concerning the use of oral contraceptives have largely been laid to rest as result of numerous studies that have evaluated low-dose oral contraceptives. The lingering concern regarding the safety of currently used oral contraceptives (i.e., pills with ≤35 μg of ethinyl estradiol [EE]) can be explained in part by the results of numerous and well-performed studies that evaluated older and higher-dose oral contraceptives. These studies demonstrated an increase in adverse health outcomes in women who used these formulations; however, these pills are either no longer available or are rarely used. Projecting the increased risk associated with these older formulations onto users of current lower-dose pills is neither scientifically nor clinically sound. The application of evidence-based medicine principles to the evaluation of oral contraceptive safety requires the use of relevant data to assess properly the risks and benefits of current oral contraceptive use.

In an attempt to provide practitioners with the most current information, this article reviews studies on venous thromboembolic events, cerebrovascular accidents, myocardial infarction, and cancer risk in women using oral contraceptive formulations containing less than 50 μg of EE. Readers are introduced to the various genetic tests that affect women's health and that are likely to have a large role in the ability to detect and treat disease in the future.

Most of the studies evaluated in this review present level II-1, II-2, II-3, and level III data. Information is culled from nonrandomized controlled trials and observational trials including case-control and cohort studies.<sup>23 Rosenberg L., Palmer J.R., Rao R.S. , y al. Case-control study of oral contraceptive use and risk of breast cancer Am J Epidemiol 1996 ;  143 : 25

Haga clic aquí para ir a la sección de Referencias</sup> Although such studies may have less impact than well-performed randomized controlled trials (level I), the consistency of outcomes among disparate studies and other assessments of evidence-based medicine (e.g., biologic plausibility, temporality) can provide profound clinical information that can have a positive impact on health care practices. Indeed, randomized controlled trials when evaluating safety issues are difficult, if not impossible, to perform because of ethical considerations.