Oral contraceptives and cycle control: a critical review of the literature.

Abstract

Control of spotting and breakthrough bleeding and absence of withdrawal bleeding, collectively termed cycle control, is the single most important determinant of whether a new user of oral contraceptives (OCs) will continue this method. However, information about different OC preparations and how they affect such problems, including the effects of progestogen and estrogen phasing and the components of these hormones, is scant and confusing. Studies cited in this report reveal highly variable rates of bleeding problems in women taking OCs: after 6 months of OC use, the prevalence of spotting varied between 0% and 8.5%; of breakthrough bleeding, 0% and 12.2%; and of amenorrhea, 0% and 5.8%. At least some of this variation is attributable to differing study populations and cultures, study designs, and the manner in which data were collected and reported. However, methodologic weaknesses were common, often involving lack of randomization and blinding, and attrition rates were high. Despite these limitations, it is clear that the frequency of bleeding problems decreases with continuing use of OCs, emphasizing the need for patient reassurance about the transient nature of these problems. In addition, gestodene-containing preparations appear to offer better cycle control than do desogestrel-containing preparations and levonorgestrel-containing preparations better control than norethindrone-containing preparations. However, the strongest lesson to emerge is the need for more rigorous studies to adequately address questions of comparative bleeding problems, particularly with newer triphasic formulations. These conclusions underscore the importance of counseling new OC users about the possibility of bleeding problems, reassuring them that most such problems are temporary, and, that if compliance is maintained, these will not impair contraceptive efficacy.