Using them should help you get pregnantifyou know how to slide in your information, andifyour app is accurate.

Its probably best to approach fertility apps as a tool to help you keep track of fertility signs.

Even so, take the apps recommendation with a grain of salt.

The idea behind tracking your cycle is legit, but getting the details right is tricky.

Why Fertility Tracking Isnt a Perfect Science

Fertility apps are essentially a special purpose calendar.

So the four or so days before ovulation are the days when sex can lead to pregnancy.

Unfortunately, theres no easy way to tell when youre about to ovulate.

A calendar can help, since ovulation occurs about two weeks before your next period is due to start.

But even this is tricky.

Your cycles might vary in length, making ovulation hard to predict.

Fortunately, your body gives you other clues about when ovulation happens.

Another helpful clue is your body temperature, whichbumps up by half a degree or soafter ovulation.

That means these apps are just assistants.

Even if you just want to keep track of your periods, these apps are still helpful.

question that doctors always ask.

(They wereiPeriod,MyDays, andClue.)

The researchers didnt test any other cycle lengths.

We do know that youremore likely to get pregnantif you have sex during the fertile window just before ovulation.

But do apps really help you to pinpoint the dates of that window?

The app helped people conceive faster, they concluded.

Should you do it every day, every other day, or every three days?

Expert opinions sometimes differ, and an app wont help with that.

If you never have unprotected sex on fertile days, it should be very hard to get pregnant.

This is actually a really effective method,ifyou get everything right.

In theory, fertility awareness methods can be97 percent effective, on par with condoms or the pill.

Real life effectiveness can be much lower,77 percent for some methods.

Can apps help you to stay closer to the perfect-use numbers?

A recent studypublished in the Journal of the American Board of Family Medicinefound that most probably cant.

Surprisingly, Glow was last on the list, with a score of zero.

Part of the reason for Glows failing grade, researchers said, was that their methods are kept secret.

That means there is no way to tell if the app is using a method thats backed by science.

If you prefer a lower-key approach, just track your period dates.

Apps are great for that, too.

It can be cool just to use an app to pay attention to whats going on in your body.

[Correction 8/18/2016: The fertility app Dot was not developed by Georgetown University.

Illustration by Jim Cooke.