Fertility Awareness Methods Compared

How the Methods Compare at a Glance

The numbers below come from studies that used different designs and different ways of counting pregnancies. You cannot compare them straight across. All the research behind them is low to moderate quality. No method is ranked as better than another.

Headline figures only; full numbers and citations are in each method's description below and in Sources. The studies use different designs, so the numbers are not directly comparable (PI = Pearl Index, pregnancies per 100 women per year; KM12 = chance of pregnancy by 12 months). All of this evidence is low to moderate quality. *Creighton counts fertile-day intercourse separately from method failure, so a standard typical-use rate is not defined (Manhart 2013). To conceive, normal-fertility couples who time intercourse to the fertile window conceive at high rates within a few cycles (about 81% by 6 cycles and 92% by 12 cycles; Gnoth 2003, PMID 12923157). †FEMM has no published method-specific effectiveness study; it is classified as a symptohormonal method (Duane 2022, PMID 35685421) but is absent from the major effectiveness review (Peragallo Urrutia 2018, PMID 30095777), so its own rates have not been measured. No method is ranked as best.

How to Read the Effectiveness Numbers

Two things get mixed up all the time. The difference matters a lot here.

Perfect use means a couple correctly spotted the fertile days and followed the method rules exactly. Typical use covers everyone in a study. That includes couples who correctly spotted a fertile day and then chose to have sex anyway. That is not a method failure. The biology worked. The behavior changed.

Here is a real example. In the Sensiplan study, couples who had no unprotected sex during the correctly identified fertile window: 0.6 pregnancies per 100 women over 13 cycles. Across the whole group in the same study: 1.8 per 100 women over 13 cycles (Frank-Herrmann 2007, PMID 17314078). Same method. Different behavior. That is why the two numbers look so different.

The studies in this guide use three different ways to count pregnancies. They cannot be compared directly across methods:

• Pearl Index (PI): pregnancies per 100 women per year of use.
• 13-cycle cumulative probability (CP13): the share of women who got pregnant by their 13th cycle of use.
• Kaplan-Meier 12-month probability (KM12): the chance of getting pregnant at 12 months of use.

One more thing about these numbers. A large review in 2018 looked at 53 FABM effectiveness studies (Peragallo Urrutia 2018, PMID 30095777). It rated zero of them as high quality: 21 were moderate, 32 were low. That is a real limit on how certain any single number can be. It does not mean these methods do not work. It means no single number settles the comparison.

If you have ever seen a chart showing "fertility awareness" at about 24 percent failure, that row lumps together several very different approaches. Simple calendar counting, mucus-only, and full symptothermal methods are all mixed together. The number is dominated by simple calendar users. It does not describe any of the seven methods below.

One special note on Creighton. That method classifies couples who had sex on a day they correctly identified as fertile in a separate category from method failure. So a standard typical-use rate is not defined in the Creighton research (Manhart 2013). The table reflects this honestly.

The Methods in Brief

These are listed from the simplest to the most detailed in terms of what they track. That order reflects how each method works. It is not a ranking.

Standard Days Method and TwoDay Method

Both methods come from the Georgetown Institute for Reproductive Health. Both are designed to be quick to learn.

The Standard Days Method is the simpler of the two. You count cycle days 8 through 19 as fertile. That is it. The one requirement is that your cycles stay between 26 and 32 days long. If your cycles are shorter or longer than that range, this method does not reliably work for you.

The TwoDay Method asks one question each day: did I notice any secretions today or yesterday? Secretions are the natural moisture or fluid your body makes from the cervix (the lower part of the uterus). If yes, that day is possibly fertile. If no to both, it is likely not fertile. Brief training with a counselor is enough to get started.

Neither method creates a daily record that a doctor could use to look for a cycle problem. If you have regular cycles and want the least time-intensive option, these are worth looking at. If your cycles vary a lot, you need a method that reads your body's actual daily signals rather than a fixed calendar window.

Learn it: Georgetown IRH, CycleBeads.

Billings Ovulation Method

Billings tracks cervical mucus. Cervical mucus is the natural fluid your body makes near the cervix. You observe how it feels and what it looks like each day. These observations change across your cycle in a pattern that follows your hormones.

The method identifies a key marker called Peak Day. This is the last day of the most slippery or stretchy mucus. Peak Day closely follows ovulation, which is when an egg is released.

There is no device and no thermometer. The skill is entirely observation-based. A certified teacher from WOOMB International trains you in it.

Because Billings reads actual daily body signals instead of a fixed calendar, it adapts to irregular cycles, the time after having a baby, and the months after stopping hormonal medications. A large World Health Organization trial tested it across many countries and literacy levels because of this adaptability.

The mucus record matters clinically. The patterns reflect how your hormones are working. Little or no mucus can point to low estrogen or a cervical problem. A doctor trained in restorative reproductive medicine can read this record to look for things a standard office visit would miss.

Learn it: WOOMB International, BOMA-USA.

Creighton Model FertilityCare System

Creighton takes the mucus observation and makes it more precise. You use a set of standardized visual codes, like stamps on a chart, to describe what you see each day. The method defines Peak Day clearly.

A certified FertilityCare Practitioner teaches you through about eight appointments in your first year.

Creighton has the highest clinical value of any mucus-only method. It is the required charting record for NaProTechnology, a detailed medical approach to diagnosing and treating cycle problems. Your mucus patterns, Peak Day timing, spotting, and cycle length all feed into a doctor's ability to evaluate your hormones. When surgery is being considered, the chart guides that planning too.

On the effectiveness side, Creighton does not have a standard typical-use rate in the research (Manhart 2013). This is because the method intentionally separates couples who had sex on a correctly identified fertile day from those who did not. That is methodological honesty, not a gap in the evidence.

Used to conceive, couples of normal fertility reach about 98% pregnancy by six cycles of well-timed intercourse (Hilgers 1992, PMID 1479570).

Learn it: FertilityCare Centers of America, Saint Paul VI Institute.

Sympto-Thermal Method

The sympto-thermal method adds a second signal to the mucus observation: your basal body temperature. That means your resting temperature, taken first thing in the morning before you get up.

After ovulation, your temperature rises and stays higher. This rise is caused by progesterone, a hormone made after the egg is released.

Mucus tells you in real time that the fertile window is open or closing. Temperature confirms it is over. Two independent signals checking each other. The most rigorously studied sympto-thermal protocol is Sensiplan, a German method with a strict double-check rule, and that double-check is why its perfect-use numbers are so low. The effectiveness figures in the table above come from Sensiplan studies; other sympto-thermal programs have not all been measured to the same standard.

Learning takes three to six cycles with a trained instructor. The temperature record also has value for a doctor. The length and shape of the temperature rise after ovulation can show whether your progesterone response is working well. If something looks off, a trained clinician has a visible record to work from.

Used to conceive, normal-fertility couples reach about 81% pregnancy by six cycles and 92% by twelve (Gnoth 2003, PMID 12923157).

Learn it: Couple to Couple League, SymptoPro, Serena Canada.

Marquette Model

Marquette uses a small electronic device called the Clearblue hormonal monitor. Each morning you test your urine. The monitor measures two hormones: estrogen (called E3G) and luteinizing hormone (LH), which surges right before the egg is released. The monitor gives you a digital readout. You can also add mucus observation alongside it.

A Marquette-certified professional teaches you how to use the monitor and read your results. Some people find the daily digital readout easier to start with than learning to describe mucus in words. The monitor does not require the same trained observation skill that mucus charting does.

Marquette has the most clearly documented approach for the time right after having a baby. It has two published studies specifically on that transition (Bouchard 2013, PMID 23288279; Schneider 2023, PMID 37325426).

The daily hormone readout is the most detailed record of any method in this guide. It can show problems with follicle development, missed ovulation, and a short or weak second half of the cycle (the part after the egg is released). Mucus observation alone can only suggest those problems. The Marquette record can show them directly.

Used to conceive, couples using the monitor reach about 83% pregnancy by twelve cycles (Bouchard 2017, PMID 29376054).

Learn it: Marquette University Institute for NFP.

FEMM

FEMM stands for Fertility Education and Medical Management. It is a symptohormonal method, which means it combines two types of observation: daily cervical mucus charting and optional urinary hormone testing. The mucus observation draws from the Billings tradition. The hormone testing, which measures LH and related hormones, overlaps with what the Marquette method uses. FEMM brings both together in one system.

Each day you record your cervical mucus. The pattern tells you where you are in your ovulatory cycle. If you add urine testing, you get a second layer of confirmation. An instructor certified through FEMM Health or the Reproductive Health Research Institute (RHRI) teaches you both. The FEMM app supports your daily tracking and charting.

What sets FEMM apart from most other methods in this guide is its medical-management arm. FEMM-trained physicians can review your chart data, evaluate underlying hormonal or cycle problems, and treat what they find. This makes FEMM one of the most clinically integrated options available. It is designed not only to time fertility, but to surface health information that a standard cycle tracking app would miss entirely. Couples trying to conceive, women working to avoid pregnancy, and those monitoring reproductive health for other reasons all use it.

One important note: FEMM does not yet have its own published effectiveness study. Unlike Billings, Marquette, or the Creighton Model, no peer-reviewed trial has measured FEMM-specific pregnancy rates or pregnancy prevention rates in a defined cohort. Its biomarkers overlap with methods that do have published data, but those numbers belong to those methods, not to FEMM. That gap is worth knowing going in.

If cycle irregularities, hormonal questions, or a diagnosis are part of why you are exploring fertility awareness, the clinical model behind FEMM may be worth a closer look. Finding a FEMM-trained provider in your area is a reasonable starting point. You can also search for a restorative reproductive medicine clinician through Find a Provider.

Learn it: FEMM Health.

How to Choose

There is no single right answer. The best method is the one you can learn well, use consistently, and, if a doctor needs to read your chart, one that creates a record they can actually use.

• Regular cycles (26 to 32 days): all seven methods are available to you. The Standard Days Method has the lightest learning burden. The sympto-thermal method and Marquette give the most precise read of your fertile window.
• Irregular, long, postpartum, or post-pill cycles: choose a method that reads real body signals, not a fixed calendar. Billings, Creighton, FEMM, the sympto-thermal method, and Marquette all adapt to cycle changes. The Standard Days Method does not. Irregular cycles are also worth discussing with a doctor, since they can point to an underlying problem.
• You want your charting tied closely to medical care: FEMM pairs cervical-mucus observation, with optional hormone testing, with a medical-management model in which FEMM-trained physicians evaluate and treat cycle problems. It does not yet have its own published effectiveness study, so weigh that against its clinical focus.
• No devices preferred: Billings or Creighton, both mucus-only with instructor follow-up.
• Prefer a digital daily readout: Marquette measures your hormones with an electronic monitor each morning, with instructor guidance.
• You want the same chart for both avoiding and achieving pregnancy: every instructor-taught method works for both goals. If getting pregnant has been difficult, a method that creates a detailed daily record for a trained clinician is especially useful.

The effectiveness numbers in these studies all come from people who were taught by a certified instructor. Self-teaching alone does not reproduce those results. For clinical use of your chart, Find a Provider.

Where to Learn Each Method

Every method has an official teaching organization. These links go directly to each one. RRM Academy does not endorse any single method and receives no referral fees.

• Creighton Model FertilityCare System: FertilityCare Centers of America and the Saint Paul VI Institute; instructor search via the American Academy of FertilityCare Professionals
• Billings Ovulation Method: WOOMB International; BOMA-USA
• Marquette Model: Marquette University Institute for Natural Family Planning
• Sympto-Thermal Method: Couple to Couple League; SymptoPro; Serena Canada (Sensiplan is the most-studied branded version)
• Standard Days and TwoDay Methods: Georgetown Institute for Reproductive Health; CycleBeads
• FEMM: FEMM Health (Reproductive Health Research Institute)

To use your chart for clinical or diagnostic purposes: Find a Provider. RRM Academy is a 501(c)(3) education nonprofit. We do not sell any of these methods or receive referral fees.

Sources

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2. Hilgers TW et al. Creighton Model NaProEducation Technology for avoiding pregnancy. Use effectiveness. J Reprod Med. 1998;43(6):495-502. PMID: 9653695. [Figure sourced through Manhart 2013; primary full text not independently reviewed.]
3. Stanford JB et al. (CEIBA study group). Pregnancies, intentions, and fertility behaviors during use of the Creighton Model Fertility Care System at 17 United States centers. PLoS One. 2025;20(6):e0328806. PMID: 40729325. DOI: 10.1371/journal.pone.0328806
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