Maxine's Journal

Adventures of the Polka-Dotted One

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More Bad Science - Contraception and Statistics. (a.k.a. Implanon Implants: They're Fine.)
I have lots of other things to catch up with, but it seems I'm most productive when I'm angry - and this idiotic article (and a swathe of similar ones) makes me EXTREMELY angry.

So what's wrong with it?

Here's the headline: "Failure of contraceptive implants sets back battle against teen pregnancies"
and the subtitle: "Bad press surrounding 584 cases in which women trusting in Implanon implants fell pregnant is a blow to family-planning advisers"

Terrifying - 584 failures - that's got to be bad, right? Well, no.

Why not?

Because statistically, that number of 584 failures makes Implanon an AMAZINGLY EFFECTIVE contraceptive.

Let's take a look at a table of statistics about contraception - I've taken my stats from here

Type of contraception
Implanon Hormone Implant: 0.05% failure rate.
Condom: 2-15% failure rate.
Crossed Fingers (no contraception): 85% failure rate.
Number of women expected to become pregnant during one year
(out of 100)
2 to 15
Around 85
Number of women expected to become pregnant during one year
(out of 82,000)
1640 to 12,300
Around 69,700
Number of women likely to become pregnant over 11 years (out of estimated 1,000,000)
20,000 to 150,000**
Around 850,000**
*actual statistic
**this is a low estimate - stats are based on only one year of use.

Contraception failure rates are measured by the number of women out of 100 who would get pregnant over a year using that contraceptive. So as you can see above, using no contraception at all, 85% of women WOULD get pregnant. Condoms have between a 2 and 15% failure rate. That means between two and 15 women will pregnant over a year whilst relying on condoms for contraception. So if 82,000 women were using condoms for contraceptive protection for a year, between 1640 and 12300 of those women would get pregnant.

So let's just compare those condom statistics back to the headline: We are told in the article that 82,000 women per year are fitted with an Implanon implant. Compared to condoms, 584 failures out of 82,000 women is very low - far less than 1%.

But that's not the end of the story.

It's not the end of the story because the 584 pregnancies they're talking about in this article weren't over one year. They were over ELEVEN YEARS. We're talking about barely one twentieth of a percent, 0.06%.
If all of these women had used condoms instead, we'd be looking at an extra 11,716 women who would likely be pregnant due to contraceptive failure - not just once either, that's every year.
That's ELEVEN THOUSAND WOMEN! Eleven thousand lives that *haven't* been disrupted by unwanted pregnancy, because they were relying on a more effective form of contraception. If they hadn't used any contraception at all? 69700 unwanted foetuses PER YEAR. This is what happens when you put people off using safe contraceptives with idiotic scare tactics.

Yes, these women "thought they were 99% safe" - based on the number of women who have actually had Implanon fitted, they were actually 99.94% safe (equivalent to one in about 2000, vs. one in 100). I'm sure it's not much of a comfort to the women who have experienced a failure (after all, on an individual level it's no longer a statistic - you're either pregnant or you're not), and of course it would have been wonderful if they could have been 100% 'safe', but compared to around 70,000 of those same women each year who would have been pregnant if they had no contraception, that's a vanishingly small number.

It's not perfect. No method of contraception is perfect, and not everyone gets on with hormone based contraception, but it's by far the best out there. And it makes me sick with anger that scare tactics like these stupid headlines are being used to trash what is clearly the most reliable means we have of preventing unwanted pregnancy.

What's the real agenda here? I have no idea. Maybe some crazy idea that that declaring contraception 'unsafe' will put teenage girls off from having sex? Maybe a complete lack of understanding of statistics. Perhaps a misunderstanding of how contraception really works - and a belief that there's a better method out there? Currently, there isn't a better option - unless you combine several at once, eg. condoms *and* an implant, or a coil, or or whatever (and of course, implants and coils don't protect from STIs, so that's an excellent idea anyway). Sadly real science doesn't give us perfect answers, it just gives us better ones. And they're getting better all the time - or they would be, if only journalists would actually understand the information they're presented with.

- - - - -
Additional information:

If you have an implant and you're worried if it might be incorrectly fitted:

What to do if you are worried?
If you are already using the Contraceptive Implant and are not experiencing any problems you probably don’t need to worry. However if this coverage has concerned you then you can speak to your GP, Reproductive Health Clinic or call the Family Planning Association (in the UK) on 0845 122 8690.

Remember this form of contraception is more than 99% effective and for the majority of women who opt to use it they experience no problems and are happy with it as their contraceptive choice.
--from Dr. Petra Boynton's blog entry, Contraceptive Implants and Media Panics – what you need to know (click for more details)

- - - - -

Update two:

There's some more decent information at these sites (though many of them still fail to compare with failure rates for other contraceptives):


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I don't understand what it has to do with 'the battle against teen pregnancies', either. How many of the women who got pregnant were teenagers? I thought that Implanon was mostly marketed to women in long-term, stable relationships who (in theory) wouldn't have STDs to worry about, and that barrier method (possibly in combination with the Pill) was more normally advocated for young women.

There is talk of making longer term contraception more easily available to girls under 18 - clearly these statistics point out how ineffective that will be at reducing teen pregnancies. (/irony)

Yeah, implants don't prevent STIs at all, but against pregnancy? They couldn't have picked a stupider argument.

I think it's good that younger women should be able to choose from a range of contraceptive options, certainly, though I think it would be a rare young woman for whom an implant was the best option in terms of general health as well as preventing unwanted pregnancies.

There was a quite bewildering little 'think-piece' in the Evening Standard which bizarrely seemed to argue that less reliable methods of contraception are 'better' because... well, I couldn't work out why, really, except that the (female) journalist seemed to have some sort of misplaced nostalgia for anxious waits for periods and running to the GP for emergency contraception when they'd forgotten their Pill, and that somehow having an implant or contraceptive jab divorces women from their reproductive health choices.


Well said. I understand that at least some of the pregnancies (the 15 or so which have gone to trial) were not even due to failure of the implant itself - rather it had been badly placed in the arm!

*nods* I'm sure some of the failures during clinical trials may have been due to this too, of course. Even including the tiny number of fitting errors though, the implant is still stunningly effective - far more so than anything else on the market. Sadly the progesterone didn't agree with me at all, or I'd still be using it.

What I've heard, and I don't have a clear source, is that this is infact the majority of the cases, also many where the implanting machanism fails and so no implant exists at all.

A friend works in a sexual health and contraception clinic, and has been comforting terrified people all week. It's just... so utterly irresponsible.

Have linked to this in an F-word comment where they platformed a stupid article on it: hope that's okay?

That's great. :) The whole idea is to fight (or at least counterbalance) the stupid!

"What's the real agenda?"

Selling newspapers.

I'm guessing the real motivation is either what theozzardofwiz said, or what you suggested with trying to present contraception as unsafe and ineffective. My sexual education in a U.S. public school seemed aimed at scaring us out of ever having sex, and that's the only motivation I can see for the opposition we saw to the HPV vaccine.

One thing I haven't seen discussed is that the implant is very toxic to a developing foetus. When I got mine fitted, they were very insistent that I had to go on the pill or abstain from any sex (even with condoms) between the first appointment and the fitting. However, since this hasn't been mentioned, presumably the reported pregancies are due to low concentrations of the contraceptive in their bodies.

I am currently on my second implant and it's worked really well for me. I've got a wee scar on my arm from the removal process but I really can't understand how someone can end up horribly scared by the removal or not notice that it's not inserted. I read about this story via Bad Science and so was actually reassured that the implant was as effective as I was told when I got it (something like 99.9%, I believe.)

Haggis, where did you get that information?

I can find nothing on the web to support the theory that implanon is toxic to foetuses, and my own understanding (from studying biology up to degree level) is that progesterone is the body's natural means of saying 'I'm already pregnant' and preventing new implantations - the contraceptive implant contains a synthesised form of progesterone, and there is really no reason it should cause any problems for an existing pregnancy. After all, biologically, that's what it's designed to protect!
However when fitting the implant medical staff *will* be very careful to check for pre-existing pregnancies because implanon tends to stop the menstrual cycle, so otherwise symptoms of pregnancy might be put down to the implant working correctly - as far as I'm aware the big concern is about unwanted babies, not foetal toxicity.

The scarring thing both surprises me and doesn't - my own implant was removed in a rather bizarre manner, and I'm not sure the woman was competent. I can easily imagine a removal even slightly less pleasant than my own causing some nasty tears. Though for such a tiny object, it really should have been a simple process.

From memory, there were court cases (possibly in Australia?) where the children of women who were pregnant before they had the implant fitted had birth defects. I can't find where I read it but, as far as I can remember, it was a reliable-seeming site, not one that was scaremongering or sex-negative. However, as in this case, it was a relatively small number of cases and the problems could be avoided by confirming that you weren't pregnant.

When I had the second one fitted (after I read about the court cases, it didn't put me off), they made much more of a big deal about confirming that I was not currently pregnant and making me take the pill for the next few weeks.

The Implanon website states that it is not suitable for women with "known or suspected pregnancy" and that "Pregnancy must be excluded before inserting IMPLANON®."

Re scarring - actually, I can see if it was inserted really badly, it could cause muscle/nerve problems and that if it's removed badly, it's a fairly visible place to have a scar.

I'm on my fourth implant. Had plenty of sex which would certainly result in pregnancy without it!! ;)

I was given a pregnancy test before they put my last one in earlier this month, even though I was swapping them out. My doctor said it was merely to "tick the boxes". Kinda glad really, my boobs had been a bit tender and my workmates were convinced I was pregnant. I knew I wasn't though, I trust my implanon implicitly. 9 years, no problems!

(For what it's worth, I'm in Australia)

The worst side effect that I'm aware of after so many years of use is that when it's getting close to the 3 years, I start getting weird periods, sometimes they're really gross. They can be light and last a month, or they can be almost brown and smell disgusting and last a week or two. Other times they're light, normal and last a few days. I've discussed this with various doctors, there's nothing bad going on. I've found ways to work around it if the need is there, so it's just annoying more than anything.

If there any other side effects, I've been living happily with them!

I highly encourage people to at least give it a go. My contraception for 3 years took a small amount of time and cost $50.

9 years, so many opportunities, zero failure

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