Comparative effectiveness of 21-day and 24-day regimens of oral contraceptives

January 01, 0001

Comparative effectiveness of 21-day and 24-day regimens of oral contraceptives

These German authors estimated real-life effectiveness of oral contraceptive pills by progestogen, length of pill-free interval, and body mass index while focusing on the effect of progestogens with a long half-life and on 24-day oral contraceptive pills regimens. They utilized outcome data from 52,218 U.S. participants in the International Active Surveillance of Women Taking Oral Contraceptives—a large, prospective, controlled, noninterventional, long-term cohort study with active surveillance of the study participants—were used to analyze contraceptive failure in association with oral contraceptive pills use. Low loss to follow-up was ensured by a comprehensive follow-up procedure.

They found: "Analyses are based on 1,634 unintended pregnancies during 73,269 woman-years of oral contraceptive pills exposure. Life-table estimates of contraceptive failure for a 24-day regimen of drospirenone and ethinyl estradiol and 21-day regimens of other progestogens were 2.1% and 3.5% after the first study year, and 4.7% and 6.7% after the third year. The adjusted hazard ratio was 0.7. Direct comparisons of the 24-day and 21-day regimens of drospirenone and norethisterone, respectively, showed also lower contraceptive failure rates for 24-day regimens. Contraceptive failure rates adjusted for age, parity and educational level showed a slight increase with higher body mass index."

The authors concluded: "The 24-day oral contraceptive regimens containing a progestogen with a long half-life show higher contraceptive effectiveness under routine medical conditions compared with conventional 21-day regimens. Obesity seems to be associated with a slight reduction of contraceptive effectiveness."

24-day regimens are associated with increased oral contraceptive effectiveness.

For the full abstract, click here.

Obstet Gynecol 117(1):33-40, January 2011
© 2011 to the American College of Obstetricians and Gynecologists
Effectiveness of Oral Contraceptive Pills in a Large U.S. Cohort Comparing Progestogen and Regimen. Jürgen Dinger, Thai Do Minh, Nina Buttmann, Kristina Bardenheuer. Correspondence to Dr. Dinger: [email protected]

Category: W. Pregnancy, Childbirth, Family Planning. Keywords: oral contraceptives, progestogens, drosperinone, norethindrone, prospective cohort study, journal watch.
Synopsis edited by Dr Linda French, Toledo, Ohio. Posted on Global Family Doctor 11 January 2011

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