Dear Hump Day,

So everyone knows that birth control is 99.7 percent effective with perfect use, 92 percent with average use, condoms are 98 percent blah, blah, blah. But what I’m wondering is: What does this actually mean? The best I can come up with is that with perfect use an average couple that has sex an average number of times with perfect use would conceive a child .3 percent of the time. How often does an average couple have sex? What exactly do those effectiveness rates mean? And why are the answers to these questions so hard to find?

Thanks,

Don’t Wanna Be A Baby Daddy

Dear DWBABD,

Effectiveness ratings are based off of studies on the ways and rates that people use contraception. So, when testing for condom effectiveness, for example, researchers gather hundreds of people for a study. For some studies they choose couples who are serodiscordant, which means one partner has HIV and the other doesn’t. Other studies look at couples who are currently not pregnant. The researchers then ask the couples to record how often they have sex and how often they use protection (if any).

The average adult in America had sex 59.6 times in 2004. That’s a little more than once a week or almost five times a month. Perfect use is based off of those people who recorded using a condom perfectly (putting it on correctly, using it only once, removing it correctly) EVERY time they had sex. Typical use is based off of those people who didn’t use the condom correctly and/or consistently. Sometimes they used it, sometimes they didn’t.

So for perfect using couples, the rate of effectiveness for pregnancy is 98 percent, meaning in one year, the average amount of couples that will get pregnant will be two in 100. For typical users of condoms, the rate is 85 percent, meaning 15 couples out of 100 will get pregnant in one year. The majority of effectiveness ratings are based off of pregnancy testing.

For HIV effectiveness, a two year study found that those who used condoms perfectly (correctly and consistently), none of their partners became infected, as opposed to those couples that admitted to typical use, 10 percent of partners became infected with HIV.

Now, by using two methods (hormonal and barrier) you’re protecting yourself and your partner from not only pregnancy but also from sexually transmitted infections. Using two methods also decreases the chance of pregnancy happening, as it is more unlikely that both methods will fail on you. Dual method is not considered a good option with multiple condoms, as using two condoms at once can lead to more friction and potential tearing. Unfortunately, the research on dual method failure rates has eluded us. There are studies that have looked at how often people use dual methods, but they tend to focus on samplings of who uses what and not on the rates of effectiveness.

To try to answer your question from a theoretical standpoint: Pregnancy begat by penile-vaginal intercourse occurs in three steps. The woman ovulates. Sperm is introduced into the unprotected vagina and then swim up north to the egg. One lucky sucker fertilizes the egg and the fertilized egg then travels to the uterus where it implants into the uterine wall. Viola! Pregnancy. In order to prevent pregnancy one should stop one of those steps from occurring.

So, hormonal birth control works to prevent ovulation, thicken cervical mucus (making it harder for sperm to reach the fallopian tube where the egg is waiting) and, theoretically, thin the uterine lining (studies have not been quite clear on how effective this last step is). That’s why, when taken perfectly, it’s so effective. Condoms on the other hand only prevent fertilization; if the condom breaks, the sperm can try to go after an egg if it has been released.

If you are actively preventing more than one step (condom plus hormonal birth control), then you’re lowering your chances of an unintended pregnancy. How much lower? We don’t know for sure. The big assumption is that these events are independent; that is, statistically speaking, the failure in the use of one birth control does not affect the failure of the other.

We would wager the math is something like this:

Method A = 92 percent effective, 8 percent failure rate (.08)

Method B = 89 percent effective, 11 percent failure rate (.11)

Using both Method A & B together will reduce the failure rate to .08 * .11 = 0.0088 or 0.88 percent. Which gives us a 99.12 percent overall effectiveness.

Why are effectiveness rates hard to find? The studies are typically published in academic journals which are usually not open to the non-paying public. Research also takes time. Results must be reported by actual people using methods in real life, over long periods. Checking out reputable sexual health organizations such as Planned Parenthood, Advocates for Youth, SIECUS and even the CDC can give you much of the information that you are looking for. Or you can just ask us.

Sex, while pleasurable and great, can potentially have some side effects if precautions aren’t taken — like babies, infections and disappointment. Be prepared, DWBABD. As long as you are taking all the precautions that you can — Planned Parenthood and UHS offer free condoms and birth control for prices much lower than regular pharmacies — and not just using a condom every third sex act and the pill on weekends, you’ve got a great chance of being able to plan a pregnancy and protect yourself against sexually transmitted infections. Have fun with it — go out and get a glow-in-the-dark condom!

This article was written by Suzie Baker and Nicolette Pawlowski. Suzie is a sexual health education coordinator and wanna-be homemaker and Nicolette is a sexual health educator and a graduate student in EPS. All questions are from real readers. Keep ’em coming! E-mail [email protected].