Hidden dangers lurk in contraceptive mobile apps

There’s been a lot of noise about a contraceptive app and I’ve waited till it’s all calmed down to write about it.

You feed in a lot of data to rate your daily chances of conception (or the opposite) with a traffic lights system.

That’s green for “go ahead and have unprotected sex” and red for “oh, no you’d better use a condom”.

Would I trust it? No, not entirely. Yes, I know it will appeal, at least in theory, to women who don’t want to take the pill, have an implant, or a coil inserted, to spare their body chemical interference. But it’s complicated.

How does it work? It requires a woman to take her temperature every day – a thermometer comes with the £40 app. Sound familiar? Yes, the rhythm method, when your temperature goes up you’re ovulating (red days) and add five more red days because sperm can survive that long.

But errors could creep in if you do a workout the night before, have a hangover, smoke, have sex that morning, feel under the weather, travel or are stressed. All those mean a recording should be skipped, as body temperature may be affected, potentially leading the app to read more red days.

How reliable is it? In their latest survey the company marketing the app, Natural Cycles, looked at data from 22,785 users. The results show 8.3% of women using the app in a typical manner including slip-ups become pregnant in the first 13 menstrual cycles (the average annual number of cycles for a woman) or in a year. About the same effectiveness as the pill at 9%.

In comparison, figures for typical use of condoms is about 18%, the implant is about 0.05%, with traditional fertility-awareness methods at 24%. But experts still say Natural Cycles’ figures should be viewed with caution. “This is an utterly self-selecting group of women,” says Dr Sarah Hardman, of the Royal College of Obstetricians and Gynaecologists.

“A lot of them will be the early adopters, the ones who were going out looking for something different, perhaps because they have had a problem with hormonal contraception – they are very motivated.”

And not everyone believes apps will bring greater sexual freedom.

“It is hard to be free with your body when it requires a very regimented sexual lifestyle,” says David Grimes, gynaecologist, from North Carolina University. So where do I stand on this novel approach to contraception?

I don’t think it’s a silver bullet and there’s probably a small group of women who’ll find it helpful but if your periods are irregular or you’re forgetful it’s probably not for you.