Safe sex statistics
July 2, 2008 7:24 AM   Subscribe

Help me convince my girlfriend that, stastically speaking, a correctly-used condom is an adequate form of birth control!

My girlfriend has her doubts about the efficacy of condoms and is very nervous that there is some possibility of pregnancy to the point that after sex she even panics sometimes. She is, however, a logical person and so I think with the right statistic I could convince her. I've looked online for some info but haven't found a easy way to say it. Maybe some statistician or mathematician here has some nice way of putting it that will help improve my sex life and put my gf's mind at ease...

Like, if 200 couples has sex 1000 times, 1 of those women will get pregant.

I assume the above quote is wildely untrue, but for illustrative purposes only...


you have a greater chance of being struck by lightening twice on the same day that getting pregant during safe sex.

See, some format like this is what I'm looking for... (ideally one that improves, not disrupts my sex life).

Thanks a lot!
posted by anonymous to Education (41 answers total) 4 users marked this as a favorite

I can't figure out the statistics for you, but I can say that the great thing about condoms is that when they fail, by breaking or slipping off or what have you, you know RIGHT AWAY and can get the morning after pill. I have always found that very reassuring (I'd never be able to trust something like the sponge, or even a diaphram, like I can with condoms).
posted by chowflap at 7:33 AM on July 2, 2008

From Planned Parenthood:

* Each year, 2 out of 100 women whose partners use condoms will become pregnant if they always use condoms correctly.
* Each year, 15 out of 100 women whose partners use condoms will become pregnant if they don't always use condoms correctly.

Used correctly condoms roughly as effective as other birth control measures, however no birth control measure (except 100% abstinence) is 100% effective.
posted by tallus at 7:35 AM on July 2, 2008

The odds of her getting pregnant when you are using a condom are about the same as the odds of you getting a hole in one. No, wait...

Some serious statistics here.
posted by weapons-grade pandemonium at 7:37 AM on July 2, 2008 [2 favorites]

Also, if she is intensely worried, she can chart her fertility (google "ovulation chart" and she can even do it online) and abstain from sex on her most fertile days. It may help put her mind at ease...
posted by chowflap at 7:38 AM on July 2, 2008 [2 favorites]

The next time she brings it up, I'd just reply with

"Pregnant? You're worried about pregnancy? Heck, if I were you I'd be more concerned with the Herpes and Hepatitis C..."

I used to suffer from this, I was hyper paranoid about getting someone pregnant. Didn't trust condoms, problem was slightly alleviated when the g/f went on the pill. Basically it went away after not have scares for while, and with age.

Statistics may frighten her more than comfort her, and make her start doing erroneous math in her head (OMG for every 1000 times we have sex I'm sure to get pregnant 3 times!!!!). I 2nd the condom/morning after pill (if it breaks near/after ejaculation) duo.
posted by Debaser626 at 7:44 AM on July 2, 2008

If she is worried to the point of panicking, maybe you should encourage her to take hormonal birth control as well instead of trying to convince her with statistics.
It might also be helpful to talk rationally about what would happen if she did become pregnant. What would you each want and what would her choices be?
Having a plan set out if indeed she does become pregnant by accident might help her see that there isn't much to be afraid of.

If statistics are what you want, I echo tallus' Planned Parenthood sentiment, and you could rephrase it to make it sound more positive:
"98 out of 100 women whose partners use condoms correctly every time will not become pregnant."
posted by rmless at 7:46 AM on July 2, 2008 [1 favorite]

She sounds like a good candidate for birth control. Or at least having emergency birth control handy.

All methods have a fail rate. There is no 100% fix short of vasectomy for you.
posted by damn dirty ape at 7:49 AM on July 2, 2008

Well, unless you just made up some random numbers, any statistics that you would show your girlfriend would only worry her more. 15% failure rate with "typical use" isn't that great.

This is another thread on which you can read about this subject - I think the general consensus there was that condoms alone are kind of worrying.

Do you need to convince her of using just condoms because you/she do not want to use hormonal birth control for some reason? If she has had bad reactions to it, I suggest that the two of you look into the cost of splitting a Mirena which doesn't have as many side effects and is more effective than (but not as permanent as) male/female sterilization.

If you have to stick with condoms, I second what others have said about charting her fertility to make her feel more secure about condom-sex on non-fertile days. This site might be a good start.
posted by mustcatchmooseandsquirrel at 7:49 AM on July 2, 2008

She could always get a dose of emergency contraception (Plan B) to keep in the medicine cabinet, just incase the condom ever slips off or breaks; she'll have it on hand and won't have to freak out about trying to obtain it the next day.
posted by at 7:50 AM on July 2, 2008

Your approach of comforting her seems misplaced, because the statistics aren't very good.

If you use condoms normally, she has a one in eight chance of getting pregnant in a year.

If you use them perfectly, which almost nobody does, she has a one in 25 to one in fifty chance.

Do not pay much attention to used-perfectly statistics. Using them perfectly means never putting one on your dick, realizing that you have it on lube-side-in, and turning it over. Using them perfectly means that the instant you feel one break, or don't feel one break, you pull out. Using them perfectly means no bare willy in the coochie or on the coochie, ever, even for a microsecond. Using them perfectly means always and without a single exception ever pulling out promptly, while still hard, and with no leakage whatsoever, no matter how much she wants to cuddle right then.

These aren't good numbers. Neither of these numbers would reassure someone who was already panicky. If I were already panicky about it, they would make me even more resolutely super-panicky.

You should be talking to her about how you can immediately deal with a broken condom, and /or about other forms of contraception to employ in conjunction with condoms.
posted by ROU_Xenophobe at 7:52 AM on July 2, 2008 [9 favorites]

If hormones are an issue (so no pill) , she could perhaps try a diaphragm as a backup?
has a list of methods
posted by pointystick at 7:53 AM on July 2, 2008

Gah, should have labeled link - it's Wikipedia.
Also CDC has information here:
posted by pointystick at 7:54 AM on July 2, 2008

Anon, you should consider (and discuss with her) your experience with condoms. Have you ever had a condom slip off during use? Have you ever had one break? Do you know how to put them on correctly and consistently? Do you use enough lube?

If you can reassure her about those things, and the effect they have on statistics, it might help calm her. That said, the bottom line statistics aren't that great, so you may have to look more widely for a solution to her concerns.
posted by alms at 7:59 AM on July 2, 2008

Like, if 200 couples has sex 1000 times, 1 of those women will get pregant.

Assuming condoms used normally, the expectation would be more like:

If 200 couples have sex 1000 times each, we would expect about 150 of those women to become pregnant at least once sometime in that period.
posted by ROU_Xenophobe at 8:00 AM on July 2, 2008

Maybe it would boost her confidence if she looks at some of the research by condom brand, and picks the one she's most comfortable with.

I was sent this (ugly) page once. It appears to list Consumer Reports' condom evaluation. I don't know when the study was done and I believe the CR website requires a subscription for login... still, this is at least a good starting place.
posted by juliplease at 8:01 AM on July 2, 2008

Condoms are most certainly not the end-all-be-all of birth control. This is why it's often recommended to use two forms of BC. How about combining the condom with another option?
posted by katillathehun at 8:05 AM on July 2, 2008 [1 favorite]

Damn dirty ape - vasectomy is not 100% effective; in fact, IUDs like mirena are more effective and easily reversible.

Statistics will convince her of nothing. As a statistician, I would never use only condoms in a relationship. Somewhere between a 2 and 15% chance within a year of changing my life entirely? no thanks.

Seriously, doubling up on methods (good methods, not rhythm or plan B) or getting a (somewhat expensive) IUD are the only statistically comforting options.

Also, to those suggesting just keeping plan B around, remember it can have nausea/vomiting/cramping/crying side effects for some women. It would also alter her period cycle, which would freak her out even more.
posted by speef at 8:09 AM on July 2, 2008

Your girlfriend sounds like me when I was younger.

Hard cold statistic facts did nothing to help me.

I would twist them, so "each year, 2 out of 100 women whose partners use condoms will become pregnant if they always use condoms correctly" turned into "You have a gun with 100 chambers. Two of the chambers are loaded. Spin the chamber, put the gun to your head, pull the trigger."

(then again, I'm not a very logical thinker. So your mileage may vary.)
posted by Lucinda at 8:10 AM on July 2, 2008

Assuming condoms used normally, the expectation would be more like:

If 200 couples have sex 1000 times each, we would expect about 150 of those women to become pregnant at least once sometime in that period.

I think you're interpreting the statistics incorrectly, ROU. 2 in 100 women who use condoms correctly will get pregnant IN A YEAR - presumably these women are having sex more than once annually. And condoms just aren't that hard (heh) to use correctly. She really shouldn't be terribly concerned. If she is, she can use the sponge or something as well (though that's always seemed like overkill to me).

OK, I'll stop monopolizing the AskMe now. I've just thought a lot about this because it's been my b.c. of choice for about 14 years.
posted by chowflap at 8:11 AM on July 2, 2008 [1 favorite]

If she's worried about condoms, why not use condoms and a back-up device? Rational or not, her anxiety is real and it sounds like a good way to deal with the problem is with redundancy.
posted by arnicae at 8:12 AM on July 2, 2008 [2 favorites]

I won't name names, but some people's math is completely insane here. Probability doesn't have a cumulative effect, guys.

Hormonal BC has about the same effectiveness %wise as condoms. If you use more than one method, your chances of getting pregnant are pretty slim.

That said, I am a single method user and have not become pregnant once in over 5 years of regular fornication. I would suspect that other people have similar experiences.
posted by shownomercy at 8:25 AM on July 2, 2008

I don't think the issue is statistics at all, but her discomfort with taking the small risk of getting pregnant that your current method has. It sounds like a perfect scenario for a backup method.

Also, the person best suited to discuss the risks and the options with her is her gynecologist. If you can encourage her to go to the GYN and bring this up, she'll likely be more comforted by what she hears there than by statistics.

Logic doesn't always rule when the consequences of the small risk happening are as great as they are with pregnancy. Until I was on the Pill and living as a grown adult who could handle issues like unplanned pregnancy, I panicked about pregnancy just about every month. It's not unusual at all for women to want to be very cautious. I'd encourage you to respect, not minimize, her fears and work with her on finding a backup method.

Having Plan B around is an excellent suggestion, but everyone should remember that there is a 72-hour window for using it. That is fine if you know there has been a condom problem (breakage or slipping off, which are obvious) but not a help if you don't know - for instance, if there has been some postcoital leakage that no one noticed, or contact with pre-ejaculate, etc.
posted by Miko at 8:35 AM on July 2, 2008 [1 favorite]

OK, 150 of the 200 women would not get pregnant, but more than 2 would probably get pregnant.

I don't really want to spend the time doing the math thing right now. But I would just assume that for every 200 women having sex around 156 times (3 times a week for a year, a 'normal' amount), there would probably be 30 pregnancies. So for 1000 times (spread out over longer, of course), it would be more. A lot more. not comforting. at all.

You can say all you want that with 'perfect use' only 4 of them would, but perfect use is unlikely. For 'very careful' use, the number would still fall somewhere between 4 and 30.

Also, condoms are not as effective as hormonal BC, several people have linked to those numbers already.
posted by speef at 8:39 AM on July 2, 2008

Back when I researched this (2002?) Depo had the lowest failure rate.
posted by salvia at 9:03 AM on July 2, 2008

Having Plan B around is an excellent suggestion, but everyone should remember that there is a 72-hour window for using it.

120-hour, actually. 5 days. But it's more effective the sooner you take it. This page by Planned Parenthood suggests that Plan B reduces the risk of pregnancy by 95% if it's taken within 24 hours, as opposed to 89% at 72 hours, and an unspecified (but presumably lower) percentage at up to 120.
posted by spaceman_spiff at 9:09 AM on July 2, 2008

A key to good sex is that both partners are relaxed enough to enjoy it. If your girlfriend is worried about pregnancy, then that will negatively impact the quality and frequency of your intimacy. This is suboptimal in terms of getting your freak on.

Stop trying to convince her that condoms will do the job. Get a second form of birth control she feels comfortable with for pregnancy prevention and use condoms for safe sex.
posted by 26.2 at 9:11 AM on July 2, 2008 [1 favorite]

I think you're interpreting the statistics incorrectly, ROU. 2 in 100 women who use condoms correctly will get pregnant IN A YEAR - presumably these women are having sex more than once annually. And condoms just aren't that hard (heh) to use correctly.

It's difficult enough that the actual rate when used normally is eight times higher than the used-perfectly rate. Anyone should bet that when push comes to shove, they'll be in the "as normally used" column, not the "used perfectly" column.

15 in 100 women can be expected to become pregnant in a year if they use condoms with a normal error rate. The average rate of intercourse for young couples is a little over 100 times/year, so the original poster's postulated 1000 times corresponds to nine years worth of risk.

From here, it's a straightforward cumulative binomial problem: 9 trials, at least 1 hit, pi=0.15. The probability of this is about 0.77. 0.77 times 200 is about 150.

Presumably, a couple having intercourse 1000 times in a year or two, as the original poster seems to imagine himself doing, would face somewhat different combinatorics, but I couldn't find a per-fuck estimate of pregnancy risk in a couple of minutes of casual googling. I could back a rough estimate out of the original probability of 15%, I suppose, with some even more heroic assumptions.
posted by ROU_Xenophobe at 9:14 AM on July 2, 2008

Mod note: a few comments removed - really OP is looking for stats not sex alternatives.
posted by jessamyn (staff) at 9:16 AM on July 2, 2008

Get her a copy of "Taking Charge of Your Fertility." Signs of fertility are pretty obvious once you know what you're looking for (vaginal mucous with the consistency of egg whites, a slight rise in body temperature), and you can chart it if you want to keep track. The window every month in which a woman is likely to get pregnant is actually pretty small.
posted by Ostara at 9:50 AM on July 2, 2008 [1 favorite]

If your girlfriend will accept anecdotal evidence:

I have been sexually active for 20 years. Condoms were my contraception method of choice for 18.5 of those years. And: I have never been pregnant in my entire life. Not even close. And while privacy prevents me from elaborating, it's safe to say that there were rather a healthy number of encounters over those 18.5 years, so we can rule out abstinence as the reason and attribute it all to the condoms.

It's anecdotal evidence, sure, but there it is, if it helps.
posted by EmpressCallipygos at 9:56 AM on July 2, 2008 [1 favorite]

This is strictly anecdotal, but I cannot use any form of hormonal birth control due to health reasons. Mr. Adams have been using condoms as our only form of birth control for 15 years, and despite experimenting with different brands/styles/textures, have never had one break, nor have I ever had a pregnancy scare. Perhaps we're just unusually lucky, but that's (as Edith Ann used to say) the truth. If your girlfriend is able to use a backup method of BC, though, I'd definitely recommend it - better to be very safe, etc.
posted by Oriole Adams at 9:58 AM on July 2, 2008

In order to retain relevance, I'd look at the five-year never-pregnant probability. For the typical user, that'd be very close to (.88^5)~=53%. For the perfect user (which is easier to motivate once you realize how large 53% is) it's about 90%.

That is, if you use condoms correctly every time for five years, there's still a 1/10 of at least one pregnancy. Using a back-up contraception method is a good idea.

Condoms are great because they protect against many STDs, they take no planning, lead-in time, or doctor visit, and can be used discretely. This is most useful for the situation of short-term relationships (where you might be more likely to use them correctly given the possibility of STDs). For long term monogamous relationships, they are not the most powerful method, but still a good idea since odds of your partner giving you an STD are not so happy.
posted by a robot made out of meat at 10:05 AM on July 2, 2008

To approach this from a slightly different angle...

You're hoping to use logic to solve what is likely a psychological hangup.

Have you had the discussion as to what would happen if she did get pregnant? Are you both in agreement about it? If you're not (or you're not able to have such a discussion), than you shouldn't be having sex with her.

(If she's American) from the time she was fairly young, she was repeatedly told not to have sex, because she might get pregnant or AIDS and then her life would be over (either literally or figuratively). Depending on where and with whom she grew up, she got fed either a little or a lot of "birth control fails sometimes, and there's no such thing as safe sex. To really be safe, don't have sex at all.", which while technically true, is horribly overstated/oversimplified (and all too often doesn't also include an honest discussion of birth control to go alongside it). This is a terrible message to be feeding teenagers, because while it does arguably delay the first sexual experience (and that is the goal), it creates adults that take years to relax enough to enjoy the beauty that is sex.

So... work on this. Talk about this. Get more relaxed about this, together. See if you can go from "Sex often has dire consequences" to "Pregnancy has (currently undesirable) consequences, and I know what we'd do in that situation". Then you're in a much better place to talk about what constitutes a reasonable level of pregnancy prevention, and how the two of you can achieve that. That's when the respective failure rates will start to become useful.

And yes, get a backup form of birth control... keeping plan B stashed away somewhere is a good idea, and having some foam with a plunger isn't a bad idea either. Condoms do break, but at least you know it when it happens, and can immediately start with your backup method. When it happens to you, you want to be able to be simply nervous, instead of panicked.
posted by toxic at 10:17 AM on July 2, 2008

Anecdotally, been using condoms for over 19+ years with my now-husband. Never had a failure, never got pregnant--except when we wanted to. (Have one daughter.)
posted by cass at 10:57 AM on July 2, 2008

We've been over this before.
posted by mr_roboto at 11:14 AM on July 2, 2008

I have never been able to tolerate birth control hormones. Condoms only since 1977 (?) with my wonderful, responsible partner and love of my life. Planned pregnancies only.
posted by nax at 12:40 PM on July 2, 2008

Pulling out is 85% effective when done correctly. You should tell her this. Also, use the ones lubricated with spermicide.

This might be a crazy idea, but maybe if you had a test to determine your sperm motility you can figure out how to reduce your count and, combined with condoms, she would feel better.

Maybe you can spend more time in the sauna, take up smoking, wear tight underwear, quit eating stuff with zinc and vitamins in it and ride bicycles daily on bumpy terrain.
posted by onepapertiger at 4:33 PM on July 2, 2008

Personally, I can't contemplate sex without two methods of contraception - condom and the ring, currently. I've done statistics up to the late undergraduate level, so I'm pretty familiar with the maths and what it means in real terms.

Just condoms? I would never have sex. The risk is just too high.

I'm aware that this is likely a mostly-psychological hangup. I know I'm not overly rational about it. And condoms make things awkward at times. But it's something that isn't amenable to change.

That said, hormonal bc can really mess with you something chronic. Different ones work better for different women, and it is a bit of a minefield at times. Getting the right one is occasionally rather challenging. For me, though, it makes me comfortable and relaxed enough to have sex without having a panic attack afterwards, so it's worth it.
posted by ysabet at 5:55 PM on July 2, 2008 [1 favorite]

I think ysabet is not alone in this, and I think you're girlfriend is reasonable to question the reliability of one form of birth control. I remember from health class that condoms, when used with a diaphragm or spermicidal foam, were the most effective form of birth control.

Using condoms effectively isn't that hard. You need to remember to put one on as soon as you are erect, and to avoid touching anything with the tip of your penis. Spermicide isn't that big a deal either.
posted by gesamtkunstwerk at 6:59 PM on July 2, 2008

Why not use two forms of birth control, as some people here have suggested? (Side note: why the heck doesn't everyone already use two forms of birth control?) Think about hormonal BC, as suggested, of if she's sensitive to the hormones, then an IUD? She may feel better if she has direct control over her method of birth control, too.
posted by you're a kitty! at 8:43 PM on July 2, 2008

Why would you want to convince her that condoms are great? Why not just let her go on the pill? You've experienced sex without a condom on right?
posted by w0mbat at 12:12 AM on July 3, 2008

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