RHL Commentary by Duru S. Shah
EVIDENCE SUMMARY
This review analysed data from two trials involving 849 women who used either biphasic or triphasic pills. Both trials examined different kinds of pills. One examined 1269 and 1163 user-cycles of two different biphasic preparations, respectively, and 1154 user-cycles of a triphasic preparation. In this trial, follow-up was carried out for 12 cycles. The other trial examined 533 user-cycles of a biphasic preparation and 506 and 524 user-cycles of two different triphasic preparations, respectively. The outcome measures compared were pregnancy, cycle control, side-effects and number and reasons for discontinuation. There were large losses to follow-up in both studies.
Both trials were retrieved through searches of Cochrane Controlled Trials Register, MEDLINE, Embase and Popline. Both have small sample sizes with a modest number of user-cycles. Moreover, the steroid hormone content of the pills used in the trials was variable. The sociodemographic characteristics of the women in the trials are not comparable and there were large losses to follow-up, which renders the internal validity of these trials questionable. Among the outcome measures the authors of the review could not comment on contraceptive efficacy because of the small sample size. There was some evidence of greater cycle control with at least one triphasic regimen in one trial. It is also difficult to draw any conclusions regarding intermenstrual bleeding or absence of withdrawal bleeding because of the different kinds of progestogen contained in the pills.
The full RHL commentary also includes sections on: Relevance
- Magnitude of the problem
- Applicability of the results
- Implementation of the intervention
Research
References
This document should be cited as: Duru S. Shah. Biphasic versus triphasic oral contraceptives for contraception: RHL commentary (last revised: 2 February 2006). The WHO Reproductive Health Library, No 9, Update Software Ltd, Oxford, 2006. www.rhlibrary.com
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