Fertility signs are individual biomarkers which can indicate fertility status that a woman can observe and chart. If you ask various fertility charters what are the best signs to chart, you are likely to get a wide range of answers. People often have different ideas about what fertility signs are best to chart based on how they first learned of fertility awareness. For example, many people first learn of fertility awareness through reading the book “Taking Charge of Your Fertility” (TCOYF) by Toni Weschler, which teaches a Sympto Thermal Method (STM) protocol. People also often have trouble distinguishing between primary and secondary fertility signs. For example, the fertility signs that TCOYF talks about charting are basal body temperature (BBT), cervical fluid (CF) and optionally cervical position (CP). BBT and CF are primary fertility signs, and CP is a secondary fertility signs. What that means is that primary fertility signs can be the only thing you chart and you can still reliably determine your fertility status, but secondary fertility signs must always be accompanied by a primary sign to be effectively used in fertility charting. Secondary signs should not be used as the only indicator of fertility status. So, for people who learned to chart through TCOYF, they often have a bias towards STM (BBT and CF) fertility charting. However, another primary fertility sign that TCOYF doesn’t teach is the estrogen + luteinizing hormone (LH) test results from the Clearblue Fertility Monitor. There are tests that are just LH tests (also called ovulation predictor kits or OPKs), but the LH tests should be considered a secondary fertility sign and the LH+Estrogen tests should be considered a primary fertility sign.

Three Primary Fertility Signs

These are the three primary fertility signs that have official, scientifically studied Fertility Awareness Based Method (FABM) protocols built around them:

There are official, highly effective FABM protocols for charting one, two, or all three of these fertility signs.

Pros & Cons of Charting
Various Fertility Signs

There are benefits and drawbacks to charting each fertility sign. Some will mesh well with your lifestyle and routine. Some may feel overly burdensome to chart. There’s no one, universally perfect set of fertility signs to chart for every woman. Finding what will work best for you individually is what’s most important. However, sometimes you actually have to just give it a go and try charting the fertility sign to ultimately see how well it will work with your individual routine and lifestyle.

  • Basal Body Temperature
    Basal Body Temperature (BBT) is measured by taking your temperature using a BBT thermometer (also called a basal thermometer or ovulation thermometer), which is sensitive enough measure a change of +/-0.1F or +/-0.05C. For a basic, inexpensive, reliable BBT thermometer, Mabis is a great option. A common favorite among fertility charters is the mid-range priced iSnow, because it is backlit and stores many days worth of temperature data. For high end, expensive thermometers, you have options like the Wink by Kindara, which will sync via Bluetooth with your phone, and Tempdrop, which is a wearable. The difference in price of BBT thermometers is related to convenience features and not in the accuracy of the thermometer. When you take your temperature manually (i.e. not using a wearable) it should be taken first thing when you wake up in the morning (before getting out of bed, talking, drinking, etc.) at approximately the same time every morning. BBT as a biomarker can let you know when ovulation has passed, meaning there is a change in temperature for this cycle to indicate what is happening. However, there is nothing inherent in any given temperature, no biomarker sign, to let you know when you are becoming fertile. There is a studied, statistical calculation that BBT protocols can use, based on past cycle data and general statistics of women, to determine likely safe days in the beginning of your cycle. Overwhelmingly this calculation is usually correct, because overwhelmingly bodies typically follow a predictable cyclical rhythm. However, in the unlikely event that you have an unexpectedly early ovulation (for whatever reason), your temperature readings will not be able to alert you to the fact that you are becoming fertile earlier than expected. Only in retrospect, when it is too late, will you learn of the early ovulation. So, with BBT the beginning of the fertile window is calculation based and the end of the fertile window is biomarker based. BBT can be thrown off by lack of sleep, different waking times, traveling, and sickness. If you’re running a fever, it’s pretty much across the board that your BBT reading is useless for that day. With sleep disruptions and travel there’s more variability from woman to woman whether or not your readings will be reliable. Cross checking helps to clarify this. BBT should not be used as the sole indicator of fertility status postpartum before the return of your regular cycles, however it is an excellent cross check during that time. With reliable BBT readings, your BBT pattern is an extremely reliable and clear indication that ovulation has passed. Check out sections that list Basal Body Temperature Methods in my List of FABMs for more information about protocols for charting this fertility sign.


  • Cervical Fluid
    It’s true that many women feel most uncertain about observing cervical fluid (CF), also called cervical mucus (CM). However, CF is the only fertility sign that can give you a biomarker indication (without a calculation) of both the beginning and end of the fertile window. It’s also the only fertility sign that you don’t need any other device or test to measure. All you need is the knowledge of what you’re looking for and what that means about your fertility. Once you understand that, the knowledge is with you for life. However, for many women CF observations can feel more ephemeral and subjective, because it is based on an individual woman’s ability to discern her own observations. At the same time, however, CF is usually the best real-time outward indication of exactly what your hormones are doing at any point in your cycle. Even if you ultimately choose not to chart CF for family planning purposes, learning to understand your individual CF pattern is important body literacy information in my view. If you are having trouble understanding your individual CF pattern, I highly recommend working with an instructor. With CF you need to observe every time you go to the bathroom and it is also important to consider sensation as you move around throughout the day. Different CF protocols place different levels of importance on stretching, visual appearance, sensation, and internal versus external checks. CF can often be confused with seminal fluid and arousal fluid. So, you need to be aware if those are possible confusing factors when making your final CF determination for the day at the end of the day. Again, cross checking can often help to clarify what your observations are telling you about your fertility status. As with any fertility sign charting for avoiding pregnancy, when in doubt always assume you’re fertile and if you are working with an instructor, check with your instructor if there is any confusion. Many women find working with an instructor greatly improves their confidence and effectiveness with their CF observations. Check out sections that list Cervical Fluid Methods in my List of FABMs for more information about protocols for charting this fertility sign.


  • Estrogen + Luteinizing Hormone Tests
    (Clearblue Fertility Monitor test results)
    With using the Clearblue Fertility Monitor (CB monitor), it’s important to use it with an official FABM protocol and not just follow the read outs from the monitor as your sole indicator of fertility status. So, using a FABM protocol for the CB monitor is basically like a combination of calculation and biomarker. For example, a Low reading on the CB monitor may not consistently give women in regular cycles enough days warning of impending ovulation to effectively avoid pregnancy. So, there’s a calculation (similar to the BBT beginning of fertile window calculation) to give women an edge day. When trying to avoid pregnancy, if a woman gets a High reading on the monitor before the edge day, then she assumes she’s fertile. If she gets a Low reading after her edge day, she still assumes she’s fertile, because it’s after the edge day. The edge day is the calculation and the CB monitor reading is the biomarker. To chart this sign you need a CB monitor. You can use either the old style or the new style with the touch screen. You will also need CB monitor test sticks. Both the old and new style monitors use the same test sticks. The major drawback most people have to using the CB monitor is the ongoing costs of buying the test sticks. However, this is a really clear fertility sign that is easily observable and not thrown off by travel, lack of sleep, etc. You just test on the days the protocol indicates to test, get the result, and follow what the protocol says indicating fertile or infertile for the day. There’s no checking anything throughout the day. It’s just one test and you know your fertility status for the day. Also, for testing with the CB monitor, there’s a 6 hour testing window. It is recommended that you start testing by using first waking urine, but there are modifications that can be made by working with an instructor to allow you to test in the afternoon or evenings if you need to. There is more flexibility in the CB monitor protocols for when to test, which is not as rigid as the routine recommended for getting a reliable BBT reading for the day. If you have a history of hormonal disfunction, such as PCOS, then you will want to discuss this history with an instructor before committing to relying on a CB monitor protocol for birth control to clarify if this will be an effective fertility sign for you to chart. Check out sections that list Hormone Monitor Methods in my List of FABMs for more information about protocols for charting this fertility sign.

Secondary Fertility Signs

These secondary fertility signs have been studied to be useful fertility signs for the vast majority of women, however they must be combined with an official FABM protocol, which has you charting at least one other primary fertility sign.


  • Cervical Position
    This is where a woman physically palpates her own cervix to determine height, how firm or soft, and the openness of the cervix. A low, firm, and closed cervix indicates low fertility, and a high, soft, and open cervix indicates high fertility. There is no official fertility charting protocol for charting this sign alone. This fertility sign should NOT be used as the sole indicator of fertility status, but may be used as a complementary, cross check fertility sign. This sign is commonly suggested as an optional cross check to Sympto Thermal Method (STM) charting. A good resource for better understanding the changes of the cervix is the Beautiful Cervix Project.
  • Luteinizing Hormone Tests
    (also known as LH tests, ovulation tests, ovulation predictor kits, or OPKs)
    This is an at-home urine analysis tool, which measures if a luteinizing hormone (LH) has reached a certain threshold to indicate ovulation is likely to occur in the next 24-36 hours. Recommended brands of LH tests are: Wondfo, ClinicalGuard, and Clearblue. Positive LH test results do not confirm definitively that ovulation happened, only that your body is producing the correct hormones at the correct levels for ovulation to happen. For women of normal hormonal function a positive LH test result is an extremely strong indicator that ovulation will happen. However, for women who experience hormonal disfunction, such as PCOS, they may experience a positive LH test without actually ovulating, or they may see multiple, seperate LH surges before finally ovulating. LH tests can be really helpful in learning how to use your fertility charting to understand your inner hormonal activity. Please contact me if you would like to know more about how to identify healthy patterns or health problems through fertility charting. Check out the sections that list Luteinizing Hormone Test Methods in my List of FABMs for more information about FABM protocols that use this sign as an official cross check.
  • Progesterone Tests
    (also known as Pregnanediol Glucuronide tests, PdG tests, Ovulation Double Checks, or ODCs)
    This is an at-home urine analysis tool, which measures if Pregnanediol Glucuronide (PdG) has reached a certain threshold to indicate ovulation has passed. The recommended brand is MBF Fertility, which developed the PdG test. PdG is the major urine metabolite of Progesterone. The presence of PdG in urine has been shown to directly correlate with the presence progesterone in serum (blood). A positive PdG test result indicates that a woman is likely in her luteal phase, but a single test does not by itself confirm that ovulation definitely happened. However, PdG tests can be used as an effective cross check with an official FABM protocol.
  • Electrolyte Testing
    (also known as saliva and/or cervical fluid electrolytes, ferning microscope, ovulation microscope, or OvaCue Fertility Monitor)
    In these methods women use a device or microscope to determine changes in electrolytes of saliva and/or cervical fluid. Some women can use these methods as a reliable cross check. However, the reliability of electrolyte charting is not consistent across all women. These methods are better to be used when trying to conceive instead of when trying to avoid pregnancy, and again, should only be used as a cross check and not the sole indicator of fertility status. Check out the section that list Electrolyte Methods (Saliva Ferning / Cue Method) in my List of FABMs for more information about charting this fertility sign.

Other secondary fertility signs, which may be useful to some women individually, but are less likely to be consistently useful from woman to woman include things like ovulation pain (mittelschmerz), breast tenderness, mood changes, and various health symptoms.

Cross Checking

So, now let me talk about cross checking. Cross checking is when you chart multiple fertility signs and they all need to be indicating the same fertility status for you to consider yourself fertile or infertile. The most commonly practiced cross check method is the Sympto Thermal Method (STM). For example, TCOYF teaches a STM protocol, but there are multiple, distinct STM protocols. STM has women charting the two primary signs of BBT and CF. The CF will give you an indication of possible early ovulation and when you are most fertile in your cycle. BBT can calculate an edge day that you can use to be more conservative about the beginning of your fertile window (basically deciding you won’t use dry days past your edge day). BBT can also help clearly determine the end of the fertile window and you can be more certain about it with making sure you CF observations match what your BBT readings are telling you. The method that FEMM teaches is a CF+LH test cross check protocol. In this method CF gives you an indication of when you are becoming fertile and CF+LH test have to agree to indicate the end of the fertile window. The benefits of cross checking is if for whatever reason one fertility sign is not correctly indicating your fertility status (which could be through incorrect observation techniques), for example if one sign is falsely indicating that  ovulation has passed and you are now infertile, it is much less likely that you will have multiple fertility signs that will give you the same, false indication. It’s basically like a back up or failsafe. If your cross checked fertility signs are not lining up reasonably well each cycle, then that is a great indication that more investigation needs to be done to look at things like your observation techniques (are you temping correctly, using the CB monitor correctly, identifying you CF correctly?) and consider that there may be a hormonal dysfunction to treat if you are accurately charting your fertility signs. The drawback to charting multiple fertility signs is that sometimes it can feel cumbersome to keep up with multiple charting routines. Also, when charting three or more fertility signs it can have the effect of unnecessarily lengthening your fertile window, which can be frustrating if you are charting to avoid pregnancy. Normally, cross checking two fertility signs is reasonable balance between safety and flexibility.

What about your period?

I absolutely consider one’s period a fertility sign. It’s important to chart your period, because that lets you know when a new cycle starts and it can also give you information about the hormonal health of your previous cycle, however charting your period alone is not enough information to let you know things like:
      • if you are actually ovulating, just because you have a period doesn’t mean you are ovulating
      • that you are fertile and about to ovulate, just because your cycle is regularly 28 days doesn’t mean that you definitely ovulate on day 14
      • that you have ovulated and are now infertile, if you are not charting individual biomarkers, like the three primary fertility signs, then it is not possible to know when you specifically and individually are fertile and infertile each cycle

There are FABMs that rely on the statistical likelihood of fertility status at any given time in the cycle. These method are generally referred to as Calendar Based Methods. The most well known of those is the outdated Calendar Rhythm Method. However, there are modern, effective calendar based methods, but they are still not as effective as charting individual biomarkers and they will not be able to indicate an earlier or later ovulation than expected. Check out the section titled “Simplified Methods” in my List of FABMs for more information about Calendar Based Methods.

How Do I Use This Information?

Now that you know more about what’s involved with charting different fertility signs, you should be able to go back to my Super Long List of Fertility Awareness Based Methods and make a more informed choice about which method will best fit your lifestyle and routine for the season of life you are in right now. If you have just had a baby and you haven’t gotten your regular cycle back, please check out my post on Postpartum Birth Control Options, because that is a unique season in your fertility and your options are different during that time than when you are in regular cycles. If you’re still feeling a little overwhelmed with all your choices, please feel free to contact me. We can work together to develop a plan that is best for you and your family for the season of life you are in right now. 


Need help figuring out which fertility signs to chart? Learn more here. :: Which Fertility Sign Should I Chart? | Starry-Eyed Pragmatist

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