FAM effectiveness rates

Fertility awareness methods (FAM) are effective, highly affordable methods of natural family planning (NFP) that are used all over the world. On this page, you will read all about the research-backed success rates of the most common, evidence-based methods of fertility awareness and natural family planning available for use today.

When it comes to selecting a fertility awareness-based method of natural family planning, there’s one question that’s of utmost importance: Does it work?

With the evidence-based FAMs available today, the answer is a resounding yes, despite what popular opinion and perhaps even some doctors would have you think.

The CDC states that fertility awareness method failure rates range from 2 to 23%. This wide range indicates that some methods are clearly more effective than others. But how can you tell which FAMs are the most effective? We will explore this question in detail below. You will find that there are a few important factors to keep in mind when evaluating which method you can trust for your individual wellbeing and the future of your family.

The difference between birth control “perfect use” and “typical use”

First, it’s important to note the difference between “perfect use” and “typical use.” The method failure rate reflects how many unintended pregnancies occurred in a clinical trial, wherein couples followed every rule to a T, with no human error; from this data, we get the success of the method with “perfect use.” Therefore, the “typical use” success rate reflects how successful the method is when used in real life, where people make mistakes of varying degrees. Note that the typical use success rate is an average calculation. It includes those who didn’t follow the rules at all on some occasions, those who made minor errors on others, and those who followed the method more or less perfectly. Your own success with the method will therefore depend on how consistently and correctly you follow the rules of your chosen method, much like the success of the birth control pill hinges on a woman taking it every day, at the exact same time.

The difference between FAM, the Rhythm Method, and calendar methods

As you start to learn more about FAMs, you’ll quickly see that there’s a whole lot more to contemporary methods of natural family planning than there is to calendar-based methods. “Calendar-based methods” is the blanket term for the rhythm method (first formalized in the 1930s) and the Standard Days method (introduced in 2002). The rhythm method is a predictive method, which uses a woman’s historically longest and shortest cycle lengths, in order to predict when she will ovulate during her next cycle. This antiquated method has not been tested with contemporary clinical designs.

The Standard Days method is for a woman whose cycles range from 26 to 32 days in length, and it predicts she’ll be fertile for days 8-19 of her cycle. With the Standard Days method, the perfect use failure rate is 4.75% and the typical use failure rate is reported as 11.96%.

While the standard days method, Cycle Beads, and apps developed from these predictive models are natural forms of birth control, they don’t provide users with knowledge of their fertility signs and the valuable health information that comes with it. These predictive methods also have lower effectiveness rates than methods that train women to observe and chart their body’s unique signs of fertility in real-time. 

Effectiveness rates of modern Fertility Awareness Methods

Contemporary, evidence-based methods of natural family planning track the various phases of a woman’s cycle each month via observable biomarkers, such as hormone levels (taken from a urine sample gathered first thing in the morning), basal body temperature (taken by mouth first thing in the morning), patterns of cervical mucus (observed during bathroom visits throughout the day), or a combination thereof. You’ll find the studies that produced the following effectiveness rates linked in the descriptions below.

The Sympto-Thermal Method (STM) combines basal body temperature (BBT) readings with observations of cervical mucus and sometimes that of the cervix itself. The perfect use rate for this method is 0.4%, and the typical use rate is 1.8%.

The Billings Ovulation Method uses cervical mucus observations to determine when a woman is fertile and when she is infertile. This universal method has been successfully taught to populations with low literacy rates, little access to technology, and even those who are visually impaired. With perfect use, the failure rate is 1%, and with typical use, it’s 10%.

The Creighton Model is another method which relies on the categorization of observed cervical mucus. Creighton uses color-coded stickers to interpret a woman’s chart. With perfect use, the method’s failure rate is 0.5%. With typical use, the failure rate is 4%.

The Marquette Model utilizes a ClearBlue Easy Fertility Monitor to track levels of luteinizing hormone (LH) and estrogen in the urine. Variations on the method use cervical mucus or BBT in conjunction with hormone readings. With perfect use, the failure rate is 0.1%; with typical use, it’s 7%. Marquette Method researchers are currently developing protocols for use of the Mira fertility monitor.

The Two Day Method is a method in which a woman asks herself if she noticed any cervical secretions today or yesterday. If either answer is “yes,” then she understands herself to be fertile. If both answers are no, she understands herself to be infertile. The perfect use failure rate is 4%, while the typical use rate is 14%. Though this method, in particular, sounds simple (and it is!), it is always best to learn any method from a trained instructor.

Comparing NFP to hormonal birth control

When you compare modern FAM pregnancy prevention effectiveness rates like those above to the rates for the Pill (perfect use 0.3%, typical use 9%), condoms (perfect use 2%, typical use 18%), and IUDs (perfect use 0.2%, typical use 1%), FAMs hold their own.

Every woman deserves to know the truth about all of the family planning methods available to her today—especially those that are low cost, with no side effects, and that can help her achieve as well as avoid pregnancy.

Click here to find an instructor in the FAM method of your choice.

Important: Natural methods do NOT protect you against STDs. Condoms decrease your risk of STDs, but do not eliminate the risk completely.

It is important to note that using condoms with fertility awareness methods during the fertile period of one’s cycle can reduce the FAM’s effectiveness rate for pregnancy prevention.

This page was last updated on March 13, 2024.