Sunday, April 10, 2005

We Don't Live In Perfect

My recent abstinence-related post has elicited this comment: [When it comes to abstinence] [t]here is no difference between perfect use and typical use. If you have sex, you are no longer abstinent. That is incorrect.

If you are using the abstinence* birth control method and you engage in sexual activity, it doesn't mean you are no longer using the method. It means you are using the method either incorrectly, or inconsistently; the very definition of typical use.

[*We are discussing continuous, as opposed to periodic, abstinence.]

Recall the definitions (emphasis mine):

Researchers have two different ways of measuring the effectiveness of contraceptive methods. "Perfect use" measures the effectiveness when a contraceptive is used exactly according to clinical guidelines. In contrast, "typical use" measures how effective a method is for the average person who does not always use the method correctly or consistently.

Let's clear up the confusion by using a case study.

Assume there are three women--one uses an intrauterine device (IUD), one uses a diaphragm, and one uses abstinence. Now, in a perfect use scenario all three methods are used correctly, and consistently.

For the IUD, correct use means a versed physician inserts the IUD properly, and its continued correct positioning is checked periodically (the woman feels for the string, the MD checks it, usually during the annual exam).

For the diaphragm, correct use means, at first visit, the MD fits the proper size, and, subsequently, the woman checks its integrity; inserts it in the proper position (covering the cervical os); uses spermicide properly (e.g., during first use, and before each subsequent ejaculation); and leaves the diaphragm in place for the indicated amount of time.

For abstinence, correct use means the woman refrains from sexual activity.

For all three methods, consistent use means the method is used each and every time sexual activity is to take place.

Of course, like the commercial says, "We don't live in Perfect". In real life (aka typical use scenario) each of our three women has two hurdles to overcome: using the method correctly, and using it consistently.

The woman using the IUD has the easiest job: assuming proper initial placement, once the IUD is inserted she doesn't have to do anything for the IUD to work. Hence, she's almost guaranteed correct use. I said "almost", because, although rare, it's possible for the IUD to become displaced [it can be expelled without the woman even knowing it; it can perforate the uterus--for the Cu T brand, the incidence is 0.6/1000 insertions].

Also, consistent use is guaranteed by the IUD's intrauterine location. In other words, since your uterus is present for every sexual encounter, so is your birth control method.

For this method, perfect use and typical use are almost the same. [One of the many reasons why, in my professional opinion, the IUD is an excellent method of birth control.]

An aside: The failure rates for perfect/typical use depend on the type of IUD used. To give you an idea, for the copper Cu T brand, the perfect use failure rate is 0.6%, and the typical use one is 0.8%. Keep these rates in mind as we'll come back to them shortly.

The woman using the diaphragm can run into problems with both correct, and consistent use. Recall all the method requirements for correct use--check for defects, proper fit and placement, time spermicide and method placement/withdrawal. In real life, it's fairly easy to miss any one of these steps, or to make a mistake. These are correct use problems.

Moreover, the woman might not use the diaphragm each and every time she has intercourse [for whatever reason--she forgets, diaphragm not handy, she's not comfortable inserting it, partner objects, etc.].

Finally, all the woman practicing abstinence has to do, to use the method correctly, is to not engage in any sexual activity. Correct use problems can crop up because there might be confusion about, or different interpretations of, what constitutes "sexual activity", etc.

Also, she might run into problems when it comes to consistent use. Like the woman using the diaphragm, she might not abstain each and every time [for whatever reason].

Another aside: So, for the Cu T IUD brand the failure rate is 0.6% with perfect use, and 0.8% with typical use. Compare this with the [combination] Pill's failure rates: 0.1% with perfect use, and 5% with typical use.

The Pill has a lower perfect use failure rate than the IUD. However, the IUD has a lower typical use failure rate. Why? Because in real life it's much easier to use the IUD correctly and consistently. You can't forget "to take" the IUD, nor can you "run out" of it. [Incidentally, for the diaphragm (with spermicide) the failure rates are 6% with perfect use, and 20% with typical use. For continuous abstinence, the perfect use rate is 0%; the typical use failure rate is unknown.]

This is a good illustration of the "just because a method has a low perfect use failure rate doesn't mean its typical use rate is equally low" concept. You cannot guess the typical use failure rate from the perfect use rate. And, without knowing the typical use effectiveness, you cannot make an informed decision about which method of birth control is best suited to your particular circumstances.

Just because you know how to use a method correctly--you know how to insert the diaphragm properly, you know abstinence entails not engaging in sexual activity--does not mean you will actually use the method correctly. Neither does knowing you should always use your birth control method, if you do not wish to become pregnant, translate into consistent use. [Any physician who's ever discussed birth control with a teenaged patient has had this conversation: MD "Are you sexually active?"; T "Yes"; MD "Are you planning a pregnancy?"; T "No"; MD "So, what method of birth control are you currently using?"; T (smiles demurely) "Umm...nothing."; MD "Do you know how pregnancy happens?"; T (slightly offended) "Yes, of course I do!"; MD "Well, ...?"; T (smiles meekly, blushes, and develops a sudden, and intense interest in the details of the examining room floor)]

Bottom line: Like with any other method of birth control, when you use abstinence there is a difference between perfect use and typical use. Since we don't know what this method's typical use failure rate is, any pronouncements about its effectiveness are so much rhetoric. And, when it comes to making decisions about your health [among other things], vacuous statements are a poor substitute for actual information.

Failure rates: Williams 21ed, p 1520


At 8:31 PM, Anonymous Anonymous said...

Part of the problem is that a lot of teens are taught "abstinence" means "no sex until marriage." Some of them grow up, get married, have tons of unprotected sex with their husbands or wives, and think they're protected from STDs and from unwanted pregnancy because they're "using abstinence"...

At 11:15 PM, Anonymous Anonymous said...

And then there's when you switch methods- from patch to pill in my case... taking pill every day and same time, yet I'm due at the end of June! (not unhappily, just unexpectedly!)

At 12:39 AM, Anonymous Anonymous said...

Just in case anyone's interested. Consumer Reports just had article on birth control methods and condoms (May 05). It's nice to see a mainstream magazine treating these as the products they are instead of a taboo subject. I also thought it was kinda amusing :)

At 11:38 PM, Anonymous Anonymous said...

I'm a little confused by the post about abstinence not protecting married individuals. Are you implying that families teaching abstinence until marriage so confuse their children that they don't realize you can get pregnant if you have sex with your spouse? How condescending.

At 2:34 AM, Anonymous Orangutang said...

The thing is, if you're not using abstinence consistently, you're not using abstinence. Honestly, I don't see how you can claim that "sometimes having sex" is just "an incorrect application of not having sex."
Abstinence education is clearly ineffective. I'm not arguing that. But you seem to think that abstinence education's failure is due to abstinence being "used typically," when really it's just not being used.
Abstinence is not having sex. If you're having sex, you're not not having sex. So you're not abstinent.
An analogy: Breathing is an effective means of getting air into your lungs. If you're not getting air into your lungs, you're not breathing. We don't say that breathing is an ineffective means of getting air into your lungs.

Honestly, I'm all for sex education. Abstinence as a policy is crap. If you actually are abstinent, it works better than anything else (due to certain inalienable laws of cause and effect.) But most people just aren't abstinent, and policies need to reflect that. People should be taught how to use contraceptives properly. There's no question about that.

But there is a serious flaw in your logic which I can not let fly.

At 9:17 PM, Blogger ema said...


It's not a matter of logic, it's a matter of perfect use vs. typical use.

At 10:48 AM, Blogger Sweetrush said...

Orangutang - the point is that these people consider themselves to be abstinent, with the occasional slip up not preventing them from thinking that 'abstinence' is their method of birth control.

At 9:14 PM, Blogger Jaime said...

The way that perfect use and typical use are measured is how abstinence has a high typical use failure rate just like every other method.

Typical use is measured by asking someone---what method of birth control do you use?

Then they follow them for a year. Estimates made for typical use are the number of women reporting abstinence as their method of birth control and still get pregnant.

Obviously, they were not actually not having sex the whole time. But it is the method they say tehy used.

It is the same for the pill. Part of the reason that the typical use for the pill is relatively low is because people claim their method of birth control is the pill and then 1) miss a couple each month 2) don't take it

Typical use does not measure those who have abandoned the method altogether. But it does count those who continually say they are that method even if one month they don't finish their pack of pills.

At 10:33 PM, Blogger ema said...


The way that perfect use and typical use are measured is how abstinence has a high typical use failure rate just like every other method.

That's incorrect. All the other methods (with a few exceptions, like the barrier group) do not have a high typical use failure rate. Moreover, we have known typical use failure rates for the other methods.


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