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Fewer unintended pregnancies with 24-day OC regimens

Clinical Question:
Are drosperinone-containing oral contraceptives or 24-day regimens associated with reduced contraceptive failure?

Bottom Line:
There are fewer unintended pregnancies with the use of an oral contraceptive (OC) regimen with a progestogen of long half-life, such as drospirenone or norethisterone, when taken for a cycle of 24 days plus 4 days as compared with the standard 21 days plus 7 days (LOE = 2b)

Dinger J, Minh TD, Buttmann N, Bardenheuer K. Effectiveness of oral contraceptive pills in a large US cohort comparing progestogen and regimen. Obstet Gynecol 2011;117(1):33-40.  [PMID:21213475]

Study Design:
Cohort (prospective)


Outpatient (primary care)

This is a report from a large cohort, the International Active Surveillance of Women Taking Oral Contraceptives, funded by Bayer Schering Pharma, Berlin, the manufacturer of a drosperinone-containing OC formulation with 24 days of active pills followed by 4 days of marker pills. This report includes 52,218 US women and 99,382 woman-years of observation. Participants were asked to complete mailed questionnaires biannually for up to 5 years. The study began enrollment in 2005, the mean age at enrollment was 26.3 years, and the loss to follow-up was 7.1%. Predefined confounders included age, body mass index, smoking, parity, and education. There were 1634 unintended pregnancies of which 229 (14%) were unassociated with conditions of noncompliance; the remainder reported conditions such as forgetting pills, the use of antibiotics, and episodes of diarrhea or vomiting. Contraceptive failure rates for drosperinone-24, drosperinine-21, and all other OCs were 2.1%, 2.8%, and 3.5%, respectively, after 1 year, and 4.7%, 5.4%, and 6.7%, repectively, after 3 years. Specific comparisons showed hazard ratios (HRs) favoring drosperinone-containing regimens and 24-day regimens as follows: HR = 0.8 for drosperinone-24 vs drosperinone-21; HR = 0.7 for drosperinone-24 vs norethisterone-24; HR = 0.7 for drosperinone-21 vs norethisterone-21; and HR = 0.8 for norethisterone-24 vs norethisterone-21. Safety issues were not addressed in this report.


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