Oral contraceptives and adolescent women: Dose versus compliance

Abstract

<h3>Background</h3> According to statistics Canada, – 40% of teenagers seeking abortion in 1995 were using contraception at the time of conception. Among them – 25% were using oral contraceptives (QC's), suggesting contribution ofboth user and method failure to unplanned pregnancies. Does the use of "low dose" pills contributes to the failure rate of OC's in teens with poor compliance or missed pills?. This report reviews the physiology of fertility suppression by combined QC's and relates this to escape ovulation when pills are forgotten. <h3>Methods</h3> Studies on the effect of QC's on fertility, specifically on ovarian activity and reproductive hormone profiles were reviewed. Simultaneously articles on contraceptive methods and user failure were tracked along with studies on contraceptive compliance. <h3>Result</h3> Ethinyl estradiol is the estrogen used almost exclusively in combination QCs. The estrogen component was thought to improve cycle control rather than add to contraceptive efficacy, although evidence suggests a synergistic effect with progesterone in ovulation suppression via the hypothalamic-pituitary-ovarian axis regulation. With a constant dose of progestin, a lower estrogen dose decreases the suppression of FSH. Progestins alone could suppress ovulation effectively, but the different progestins appear to significantly differ in their potency (gestodene=desogestrel > levonorgestrel > northindrone) and circulating half-life (northindrone 8hr, levonorgestrel 10–13hr, desogestrel 12–26hr). Ovarian activity as measured by follicular size is lowest with desogestrel QC's and greatest with triphasic/monophasic levonorgestrel and norgestimate OC's, however all preparations suppress ovarian activity and prevent ovulation when taken appropriately. In those women who conceive while on QC's, method failure was a marginal problem (12%) whereas user failure was more contributing (88%). The literature on the "quality of use" (compliance) suggest that between 30 to 35% of women forget at least one tablet per cycle and only 20% manage to take their pill at the same time every day. Up to 32% of women prolonged the hormone-free period by failing to complete all the pills in a cycle and/or by delaying the start of the next packet. <h3>Conclusion</h3> All currently available OC preparations are effective in pregnancy prevention though some may not allow a large margin oferror in women who fail to take their pills with precision. If doses are to be reduced, components' potencies and half-lives should be sufficient to compensate for poor quality of use. Further research is needed to determine the risk of escape ovulation with various QC preparations in relation to missed pills.