Medically reviewed on February 17, 2022 by Jordan Stachel, M.S., RDN, CPT. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.
There are many different methods to either prevent pregnancy or to assess the ability to conceive. The group of methods known as fertility awareness methods (FAMs) relies on tracking the natural reproductive cycle to determine the most and least fertile times to conceive .
By using either calendar or symptom-based signals, fertility awareness methods can help determine the likelihood of conception at a specific time.
If you’re interested in using FAMSs to help prevent pregnancy or to conceive, it’s important to note that there are varying degrees of effectiveness. In this guide, we’ll look at the most commonly used fertility awareness methods, their effectiveness, and the pros and cons of relying on them. (To learn more about your fertility-related hormones, consider taking the at-home Women's Fertility Test.)
FAMs are divided into two categories based on how they work and the tracking method used. The two types include :
Let’s take a deeper dive into four of the more commonly used FAMs.
The “standard days” fertility awareness method is a calendar-based method of tracking the menstrual cycle and, in turn, fertility levels . In the standard days method, you base calculations on an average 26–32-day menstrual cycle length. With this average length, peak fertility days fall anywhere between days 8–19.
When it comes to pregnancy prevention, there are a few factors that make this method problematic. These include:
However, if you do wish to become pregnant, the standard days method may provide insight into which days you’re most fertile each month. Either way, the calendar method provides insight and understanding into the natural cycles.
The cervix naturally produces mucus, and the appearance and thickness of this mucus changes throughout the cycle. In the cervical mucus method, you test the cervical mucus for changes throughout the cycle. You can test the mucus by monitoring its appearance on underwear or using a clean piece of toilet paper to wipe inside the vagina.
The look and consistency of cervical mucus typically changes as follows:
It’s important to note that many factors outside of the menstrual cycle can also impact the appearance or consistency of cervical mucus. Some of these factors may include:
Some individuals also naturally don’t produce a significant amount of discharge. In these cases, the cervical mucus method is not the best fertility awareness method to use.
The "two days" method is considered a simpler version of the regular cervical mucus method. With the two days version, you ask yourself two questions each day:
If you answer “yes” to at least one of the questions, you’re probably in the fertile time for that cycle. In contrast, two answers of “no” means you’re likely outside of the fertile period.
This fertility awareness method requires a special thermometer to test the basal body temperature (BBT) each morning when waking up. Your BBT is the body’s temperature at rest, so if you’re using this method, be sure to test before you start to move around much. This means testing before you get out of bed, use the bathroom, or have anything to eat or drink.
The BBT method requires that you track body temperature for multiple months to get a clear picture of what your BBT is.
What does this have to do with fertility?
The average BBT increases slightly during ovulation. It then stays at this slightly elevated level until you finish a menstrual cycle. The temperature increase is very small—only between 0.5 to 1.0 degrees Fahrenheit—which is why it’s important to use a special BBT testing thermometer which can provide a more accurate reading.
However, the BBT method isn’t very effective because many other factors can impact body temperature, such as:
Plus, because BBT only rises after ovulation has already started, it’s not the best method for those trying to conceive.
The symptothermal method combines two or more other FAMs to track fertility. For example, some people like to pair the BBT and cervical mucus methods. If you add the calendar method to the mix, you’ll get more accurate results.
However, the same problems that can interfere with the effectiveness of individual FAMs can also occur with the symptothermal method. If you wish to prevent pregnancy, you’re better protected with either hormonal, implant, and/or barrier methods of birth control.
The effectiveness of FAMs depends on how you define the term effective. For individuals who hope to become pregnant, paying closer attention to the menstrual cycle might help them better understand when conception is more likely.
However, if you want to use FAMs to prevent pregnancy, consider other methods of birth control first. According to the American College of Obstetricians and Gynecologists, individuals who rely on FAMs for birth control have an increased risk of becoming pregnant when compared to individuals who use other methods .
If you’re trying to prevent pregnancy using FAMs, you should know:
So other methods of contraception, such as barrier methods or hormonal methods, are a better choice if wishing to prevent pregnancy.
Factors that interfere with the effectiveness of fertility awareness methods Perfection and consistency aren’t the only reasons why FAM effectiveness can vary. The CDC describes several groups of people who may experience less effectiveness with FAMs . These include:
FAMs aren’t as reliable as other forms of birth control. However, there are a few potential advantages that come with using FAMs. For example, these methods:
You’ll notice that preventing pregnancy reliably or effectively isn’t one of the advantages. This is because most people don’t use FAMs without error, resulting in poor outcomes.
There are several reasons not to place birth control methods in the hands of FAMs. According to the CDC, the disadvantages of FAMs include:
There are many more reliable pregnancy prevention tools available for people who don’t want to conceive.
Fertility Awareness Methods can help shine a light on the reproductive cycle and the time each month when conception is most likely. If you’re trying to get pregnant, this information can increase the likelihood of successfully conceiving. However, when it comes to preventing pregnancy, other birth control methods have a higher level of effectiveness.
In either situation, FAMs can help you get in tune with the body and your menstrual cycle.
At Everlywell, we understand that it’s normal to want to know how your fertility levels and bodily functions work. By testing hormones, you can get the insight you crave—no FAMs needed. In fact, with the Everlywell Woman’s Fertility Test, you can measure 5 key hormones that affect the menstrual cycle and ovulation. Plus, you can do it all in the comfort of your own home.
1. Fertility Awareness Methods of Family Planning. American College of Obstetricians and Gynecologists. URL. Accessed February 17, 2022.
2. Classifications for Fertility Awareness Methods. Centers for Disease Control and Prevention. URL. Accessed February 17, 2022.
3. Natural Family Planning. American Academy of Family Physicians. URL. Accessed February 17, 2022.