Type “period tracker app” into your phone app store, and you can scroll through more than 40 options, both free and for purchase.

There are ample reasons women use them – to track their menstrual cycles for the convenience of knowing when they’ll likely start and stop, to track ovulation to try to prevent pregnancy or to support conception (especially in their first year of trying to get pregnant), to identify patterns of frustrating symptoms and more.

With a variety of tracker apps available, you can shop for an app that will suit your goals for tracking, whatever those top goals may be. Still wondering if a period app is right for you? Here are five things to know about how using a period tracker may be useful.

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1. They can help manage mood fluctuations

Women experience dramatic hormonal fluctuations during their cycle when they’re not on birth control. And even women with IUDs can have these changes because the ovary still works in the background of an IUD.

Rather than assuming there’s something wrong with your moods, you could start to notice a pattern in the symptoms you track in your app that could coincide with rises and falls in hormones over each month.

A period app can help you track and therefore anticipate times in your cycle when you regularly experience symptoms like mood issues, or bloating, then increase your activities to prevent them. These strategies may include eating a balanced diet of high-quality foods, and ensuring you are getting enough sleep and exercise.

2. You may experience increased awareness of ovulation

If you are trying to conceive, knowing when you are ovulating is key. Ovulation is when a mature egg becomes ready to be fertilized after it is released from an ovary. This occurs approximately two weeks before the start of a menstrual period.

A woman’s chance of getting pregnant each month, depending on age, is about 25%. An app can help you track the days during which you are fertile each month. When you have an increased awareness of your fertile days, it can also help you to become more in tune with the natural body changes that occur during ovulation, such as changes in vaginal discharge as cervical mucus becomes more plentiful and stickier.

3. They’ll help you better understand ebbs and flows in sex drive

Libido can be heightened or lessened depending on where a woman is in her menstrual cycle. A natural testosterone peak occurs right before ovulation, so women often have more sexual desire for a partner when they’re most likely to conceive.

Women coming off oral contraceptives, also known as birth control pills, may notice their period doesn’t come right on time, the way it may have during years of hormonal contraception usage. An app can help track when changes in vaginal discharge and sex drive occur – good signs that the body is ovulating.

4. You can’t rely on them alone to prevent pregnancy

No matter how much data you give them, period tracker apps are not always accurate. Many offer a more data-driven way to follow the rhythm method, a type of natural family planning that relies on menstrual history to predict ovulation and to indicate windows of time where conception is most likely.

But ovulation is not on an exact schedule. You can ovulate earlier or later than predicted, and an app cannot foretell those natural variances.

5. You can use them to store notes for your doctor visits

During routine doctor visits, a clinician will check your blood pressure and weight, and ask the date of your last menstrual period. For younger women, doctors need to be aware of pregnancy risk, especially when prescribing medications or advising procedural or surgical care. This applies to women in their 40s as well, plus, at this age and up, tracking menstrual periods can help detect the beginning of the transition toward menopause (when the periods stop). Diligently using a period tracker app can help you to accurately report this information to your doctor.