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Illustration by Marta Pucci

How to Use Clue

How to use the Clue app to help you become pregnant

Track your periods, body temperature, cervical fluid, and ovulation tests.

If you are trying to get pregnant, knowing more about your menstrual cycle and fertility indicators can help speed up the process. Once you have this information, you can have sex at the optimal time for conception. If you’re having trouble getting pregnant, then tracking these things may help you figure out what might be going on.

That’s where the Clue app comes in. You can use Clue to track your cycle predictability, cycle length, basal body temperature (BBT), cervical fluid, and ovulation test results. Clue calculates your estimated ovulation day using this data.

Cycle predictability and length

If you’ve been using the Clue app and have tracked at least three cycles, you'll be able to establish a baseline for your period predictability and cycle length.

What is considered a “regular” cycle?

While most people don’t have perfectly predictable cycles, a “normal” cycle length variation is between 0-7 days for people between the ages of 26 and 41, and 0-9 days for people between the ages of 18-25 or 42-45 (1). Once you’ve learned if you have “regular” cycles, then you can start paying attention to your body's fertility window and predicted ovulation day.

Why does cycle predictability matter when you’re trying to conceive?

Cycle predictability is associated with the predictability of ovulation. If you have predictable cycles, it’s likely that you’re also ovulating around the same time each cycle. In contrast, unpredictable cycles may be a sign of an issue that can make becoming pregnant more difficult, such as polycystic ovary syndrome (PCOS), or just make it harder to predict when you might be ovulating (2).

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  • Download the Clue app on the App Store
  • Download the Clue app on the Play Store


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The importance of cycle length when you are trying to get pregnant

Cycle lengths between 24-38 days are generally considered typical (3). Very long or very short cycles may suggest that ovulation is occurring infrequently or not at all, and pregnancy may be more difficult to achieve naturally for people with these cycle lengths (4). Knowing if your cycle falls within the typical range can be useful information for planning a pregnancy.

Where can I view my past periods and cycle history in the Clue app?

To see an overview of your previous periods and cycles in the Clue app, tap on the Analysis tab (it looks like a little line graph to the right of the “+” button) and it will bring you to a screen that looks like this:

Tracking for pregnancy 1

If you currently use Clue Plus, you’ll be able to see an enhanced version of the Analysis screen. This will tell you your typical cycle length (the number of days between the first day of your period and the day before your next period starts), your typical period length (the number of days of bleeding each cycle), and the typical cycle length variation (a measure of your cycle’s changes from one cycle to the next).

What is the biological fertile window?

Your biological fertile window consists of the days leading up to, including, and immediately after ovulation. To conceive, you need to have unprotected sex during the days that you are assume you are fertile. Sex too early in the cycle or too late in the cycle won’t lead to pregnancy because there won’t be an egg to fertilize (5, 6).

How can I know when I will ovulate?

Ovulation occurs when one of your ovaries releases an egg. The egg can be fertilized for up to 24 hours as it journeys through the fallopian tubes towards the uterus. Sperm can live inside the body for up to five days before ovulation, depending on the health of the sperm and the quality of the cervical fluid.

So, if you have unprotected sex or use another form of insemination up to five days before ovulation, the sperm can live long enough to potentially fertilize the egg and pregnancy may result.  If the egg is not fertilized within this time, it passes out of your uterus with your period. Your predicted day of ovulation will look like this in the Clue app:

illustration of ovulation day in Clue

While Clue is not a diagnostic tool, paying attention to the regularity of your menstrual cycle, your fertile window, and your predicted day of ovulation can help you get to know your body better. This may be helpful if your goal is to become pregnant.

I can’t see my predicted ovulation day in the Clue app. What should I do?

To display the predicted day of ovulation in the Clue app, go to the Menu. The Menu icon is in the top right-hand corner of the Cycle View in your Clue app and looks like three dots. Tap on the icon, then tap Settings and then tap on the Ovulation tab. On this page, next to “Show potential ovulation day,” tap the toggle to turn it on. The screen will look like this:

Screenshot of the Clue app indicated how to turn on your predicted day of ovulation.

Why should I track my basal body temperature for pregnancy?

Your basal body temperature is your body temperature when you’re at rest. Your reproductive hormones have a measurable impact on your body temperature, so monitoring temperature can help you determine when your fertile window occurs.

When you track your BBT in Clue, the app is able to confirm when ovulation has occurred (after the fact). Your BBT is slightly lower prior to ovulation and slightly higher after ovulation (6, 7). After ovulation, there is a rise in the hormone progesterone, and this rise in progesterone causes a slight increase in your body temperature (7).

To get more accurate predictions of your ovulation day, you should take your temperature every day at the same time each day. It is recommended to take your BBT immediately after waking up while still laying in bed before sitting upright (6).

Why should I track cervical fluid to become pregnant?

Tracking cervical fluid is especially helpful if you are trying to become pregnant. Cervical fluid is a mixture of substances produced by glands in your cervix which acts as a protective barrier to your uterus. Cervical fluid affects the ability of sperm to travel through the reproductive tract and affects how long sperm may survive there (8). The quality of your cervical fluid affects the duration of your fertile window days.

The quality and quantity of your cervical fluid changes throughout your cycle in response to hormonal fluctuations (8). As ovulation approaches, more cervical fluid is produced and the fluid becomes stretchier, clearer, and more wet and slippery—like a raw egg white (9). (Some people also call cervical fluid "ovulation discharge").  Tracking the changes in your cervical fluid can be helpful to determine if ovulation is approaching or has already occurred.

Learning to identify the consistency, sensation, amount, and color of your cervical fluid can help you anticipate your day of ovulation. The presence of fertile-type cervical fluid alone cannot confirm ovulation.

Tracking and observing cervical fluid can increase your chances of conception—by helping you to better determine the timing and length of your fertile window days.

Note: Clue allows you to input data about your cervical fluid, but Clue’s algorithm currently doesn’t use this information to estimate the length or timing of ovulation.

Track ovulation tests for more accurate ovulation predictions

In the Clue app, you can track when you use at-home ovulation tests. There are two different types of home ovulation prediction tests/kits (OPKs) that you can purchase over the counter. OPKs either identify luteinizing hormone or the estrogen metabolite estrone-3-glucuronide (E3G) (10).

A positive ovulation test takes precedence over Clue’s prediction for your ovulation day. After entering a positive ovulation test, your cycle view and calendar will adjust accordingly. The data will also be used to derive the length of your luteal phase (time from ovulation to the day before the first day of your next period). When you track ovulation tests  this will make Clue’s period and ovulation predictions more accurate.

Can I get pregnant at any time during my cycle?

A common misconception is that you can only get pregnant on the day of ovulation, or that you can get pregnant at any old time. This is not the case—you can only get pregnant if you have unprotected sex during your biological fertile window.

If you are trying to get pregnant, use the ovulation day estimated by Clue, track your basal body temperature, and monitor your cervical fluid to have a better understanding of your fertile window—the days when you have a higher chance of conceiving.

If you are trying to prevent pregnancy, you should not use Clue’s predicted day of ovulation estimate as a form of birth control. Using fertility indicators to avoid pregnancy requires more rules and diligence, compared to using them to get pregnant. If you are not intending to become pregnant, then you should follow a formal form of natural birth control and/or use another form of contraception, like condoms, to prevent pregnancy.

Becoming pregnant is a science, and even when you become more in tune with your cycles, body temperature, and cervical fluid, sperm quality is also a factor. The more you track in Clue, the more control, and awareness you have over your own bodily functions.

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