Close-up of a young couple holding a condom

Birth control effectiveness is calculated in a manner that’s not intuitive

If a contraceptive method is 90 percent effective, some people believe they it fails 10 percent of the time, that they’re fated to get pregnant one out every 10 times they have sex using it. Actually, this is not the case.

Birth control effectiveness rates are based on “100 couple-years of regular use.” A “couple-year” represents one couple using the method exclusively for one year. If a method is 90 percent effective, ten pregnancies can be expected among 100 couples who use it for twelve months. Assuming sex once a week, 100 couples would make love 5,200 times per year, and experience 10 pregnancies, or one pregnancy every 520 times—or around two-tenths of 1 percent of rolls in the hay. Ninety percent effectiveness isn’t perfect, but it’s quite effective.

In addition, effectiveness is often expressed as two figures—theoretical effectiveness assuming perfect use, often very high, and actual effectiveness based on decades of studies that have tracked couples’ actual experiences with sometimes less-than-perfect use, often considerably lower.

Many people get scared when they see that condoms’ actual use-effectiveness is only 82 percent. That’s still quite effective. Those 100 imperfect couples who make love 5200 times a year could be expected to have 18 pregnancies, one every 289 times, or around three-tenths of 1 percent of romps—still pretty effective.

Meanwhile, studies of condoms’ actual use-effectiveness include trials whose subjects were naïve teens unfamiliar with condoms who attempted to use them while drunk. If you’re more mature, more sexually experienced, and more familiar with condoms, your personal use-effectiveness may not quite get up to this method’s theoretical effectiveness of 98 percent, but it’s quite likely to be pretty close.

The figures below come from the bible of birth control, Contraceptive Technology (20th edition, 2015) by Robert Hatcher et al.

Most people are unaware that there are almost two dozen different methods. For individual counseling about all of them, and to obtain the one that works best in your relationship, visit a family planning clinic. Most county health departments around the U.S. provide contraceptive services. In addition, Planned Parenthood operates more than 600 family planning clinics around the U.S.

Methods are listed from least to most technological.

Contraceptive Effectiveness (in 100-couple-years)

Method                           Effectiveness

No contraception             15% effective

Sex, no intercourse         100%

Withdrawal                     78-96%

Calendar rhythm             70-85%

Condom for men             82-98%

Condom for women         79-95%

Spermicides                    Alone, 72-94%. With condoms, up to 98%.

Vaginal film                    Alone, 75-94%. With condoms up to 97%.

Diaphragm                       88-94%

Cervical cap                    No kids, 80-90%. Mothers, 60-80%.

Sponge                             70-90%

Fertility awareness           80-99%

Birth control pills             95-99+%

IUD                                 99-99+%

Depo-Provera                 94-99+%

NuvaRing                       91-99%

Evra patch                      98-99%

Implanon                         99+%

Post-coital                     First 24 hours, 95%. After 72 hours, 89%.

Male sterilization           99+%

Female sterilization       99+%

Men Who Want Great Sex MUST Participate Fully in Birth Control

Great sex requires deep relaxation. If you’re not trying to conceive a child, it’s impossible for the vast majority of women—and many men—to relax when they feel anxious about an unplanned pregnancy.

Great sex also requires trust. The vast majority of women—and many men—can’t trust a lover who doesn’t care enough about unplanned pregnancy to discuss contraception beforehand.

Finally, great sex requires leisurely, playful, whole-body massage, which allows plenty of time to discuss contraception—and do something about it.

Contraception is the couple’s responsibility, not the woman’s. Raise the issue—as soon as things begin to heat up. Ideally, unless you make love without intercourse (genital massage, oral, toys) or condoms, the two of you should visit a family planning clinic, learn each method’s pros and cons, and decide which one best suits your needs—then use your chosen method every time.

Most people consider condoms the only “man’s” method, and all the others “women’s.” In fact, many contraceptives can be shared—and they work best when both lovers are involved. Sex without vaginal intercourse is a completely shared method based on handjobs and oral sex Women can roll condoms onto men’s erections. Men can buy spermicide for diaphragms, and load them. And men can check for IUD strings, and for fertility awareness, help women chart their menstrual cycles.

Birth control is not the easiest subject to discuss, particularly for new lovers. But it’s easier than talking about sexual frequency or the moves you want in bed. Considering contraceptives can be excellent practice for negotiating more challenging sexual issues

Discussing contraception doesn’t interfere with sexual pleasure any more than slowing down for a turn interferes with the enjoyment of driving. It reduces stress, encourages deep relaxation, fosters intimate communication, and builds trust—all of which enhance sex.

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