Contraceptive Pearl: The Mirage of “Perfect Use”

Many contraceptive patient information materials report two types of efficacy: that with “perfect use” and that with “typical use.” Perfect use assumes that a contraceptive method is used exactly as directed. For example, this means taking a pill daily or using a barrier method correctly with every episode of vaginal intercourse over the span of a year. Typical use, on the other hand, represents what people actually do, and includes all obstacles to adherence that occur in everyday life.

How are perfect-use contraceptive efficacy numbers established? Some perfect-use estimates rely on study subjects’ self-reported adherence, which may have less than perfect accuracy. Several perfect-use estimates extrapolate data from trials of six menstrual cycles, assuming that the second half of a year’s use would yield the same failure rate as the first half. A Standard Days Method perfect-use estimate excludes research subjects with irregular menstrual cycles and requires that couples abstain from intercourse during cycle days 8-19. A Depo-Provera perfect-use efficacy estimate pools results from nine clinical trials, excluding patients who stopped injections or received any injection late. Perfect use, it turns out, is a theoretical construct that requires significant manipulation of data and may have limited applicability to many contraception users.

No other area of medicine holds so consistently to the divide between the “perfect” and the “typical.” Reports of antihypertensive, antidepressant, and antibiotic efficacy generally rely on what, in the contraceptive arena, would be called typical use; that is, they examine efficacy measured among actual people taking a medication while going about their lives. Why does the contraceptive arena emphasize perfect use? It may be impossible to know where or how this focus originated. It’s tempting to speculate that this began with (mostly male) researchers’ condescension toward their (mostly female) research subjects.

“Perfect use” is a theoretical construct that may mislead patients. For this reason, RHAP’s educational materials now display only real-world, “typical-use” efficacy standards, the same type used in most medical settings.



Your Birth Control Choices Fact Sheet



Kaunitz AM, Portland D, Westhoff CL, Archer DF, Mishell DR, Foegh M. Self-reported and verified compliance in a phase 3 clinical trial of a novel low-dose contraceptive patch and pill. Contraception. 20159;91(3):204-210. doi:10.1016/j.contraception.2014.11.011.

Marston CA, Church K. Does the evidence support global promotion of the calendar-based Standard Days Method of contraception? Contraception. 2016;93(6):492-497. doi: 10.1016/j.contraception.2016.01.006.

Trussell J. Contraceptive failure in the United States. Contraception. 2011;83(5):397-404. doi:10.1016/j.contraception.2011.01.021.



The Reproductive Health Access Project does not accept funding from pharmaceutical companies. We do not promote specific brands of medication or contraception. The information in the Contraceptive Pearls is unbiased, based on science alone.

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