SCIENCE MARCHES ON: One of the physicists behind the Higgs boson has made an algorithm to replace the pill: It’s up to 99.5% effective at stopping pregnancy.

It’s not the first fertility app out there, but Berglund’s app works so well that it’s been shown to help women avoid pregnancy with 99.5 percent reliability – an efficacy that puts it right up there with the pill and condoms.

Best of all, the app doesn’t have any side effects, and just requires women to input their temperature daily to map their fertility throughout the month. . . .

Using a woman’s natural fertility cycle to help her avoid getting pregnant isn’t a new idea – it stems from something called the rhythm method, which is a form of contraceptive that claims to work just by having women avoid unprotected sex on fertile days each month.

In theory, that should work quite well. After all, there’s only a roughly nine-day window during which a woman can get pregnant each month. But the rhythm method is pretty unreliable, seeing as all women have slightly different cycles, and in real life, it only has a success rate of around 75 percent.

But Berglund’s algorithm is different – it uses the same advanced statistical methods she used at CERN, and is based on a woman’s daily temperature rather than simply the day of her cycle.

That’s because after ovulation, women see a spike in progesterone, which makes their bodies up to 0.45 degrees Celsius warmer.

So by entering your temperature in the app daily, and comparing the results with a broader dataset, the app lets you know when you can have unprotected sex (a green day) and when to use contraception, such as condoms (a red day).

There have been two trials so far, and the second one analysed data on more than 4,000 women aged 20 to 35 using the app.

Over the course of one year, there were 143 unplanned pregnancies in the cohort, 10 of which were conceived on green days, giving the app a 99.5 percent reliability rating. (The rest of the unplanned pregnancies were the result of women not using the app properly.)

To put that into perspective, condoms are 98 percent effective, and IUD devices are 99 percent reliable, as is the pill, when taken at the same time every day.

Of course, most birth control is much less reliable in practice than when used perfectly.