Fortunately that statistic has now been updated, thanks to an evidence review from the US Guttmacher Institute.
Some of the review jars with me. For example it contrasts typical use with "perfect" use, which is a loaded word, especially for women.
I prefer the word "correct". You don't have to be
I'm also a little tired of the implication that women should prioritise effectiveness over all other considerations when choosing contraception, including our quality of life.
It was refreshing to see the ethics of this approach challenged by a recent paper in the BMJ Sexual and Reproductive Health.
Still, effectiveness matters and it is good to see fertility awareness included in the Guttmacher review.
They replace the old 1 in 4 typical use failure rate, which lumped all the different methods together, with a new failure rate that ranges from 2% to 34% depending on the method used.
The correct use failure rating goes from less than 1% to 12%.
That's a big difference. The method you use matters.
According to the review, the most effective fertility awareness method is Sensiplan, which is a more detailed version of the Fertility UK approach that I teach.
I prefer Fertility UK as I think it's easier to use and understand. It's also the approach recommended by the NHS website.
Both methods use waking temperature, cervical fluid (“mucus”) and cycle length calculations to confirm the fertile time, and follow the guidelines described in this research study.
A key difference is that Fertility UK uses a standard Celsius fever thermometer to measure waking temperature instead of a two decimal point thermometer - also known as a Basal Body Temperature.
Some will be very comfortable with two decimal points, but I think shorter numbers make life easier, especially first thing in the morning.
Also you don’t need that much detail. One decimal point is enough to see the sustained temperature rise that means your fertile days are over.
Two decimal points might mean you see a slight dip in your temperature around ovulation, but not everyone gets this. "Look for the rise, not the dip" as Jane Knight of Fertility UK says in her Complete Guide to Fertility Awareness.
If you want a really simple approach, Guttmacher gives the Standard Days Method (CycleBeads) a correct use failure rate of 5%, which is good enough for many women. Record day one of your period and the app does the rest.
But it's probably not as much hassle as you might think to take your waking temperature, keep a vague eye on your fluid and do some basic sums.
In fact it can be pretty liberating - definitely worth taking that leap.
Find out if FAM is right for you here.