Beginner's Guide to Natural Family Planning (NFP)

What is Natural Family Planning (NFP?)

Natural Family Planning (NFP) refers to the family planning methods approved by the Catholic Church. It’s a way of managing one’s fertility without using pills, devices, or barriers.  It works through fertility awareness.

Women and couples learn how to “read” the language of their body and how to interpret their readings to help identify the fertile window (fertile days and infertile days) in each menstrual cycles.

You can use NFP to achieve pregnancy, or to postpone pregnancy. Couples who want to avoid pregnancy abstain from intercourse during fertile days. Couples who want to achieve pregnancy can engage in focused intercourse during the fertile window to increase their chances of becoming pregnant sooner.

Intercourse outside of the fertile window is naturally infertile (hence “natural family planning”). On infertile days, couples aiming to avoid pregnancy can engage in intercourse freely. 

This beginner’s guide to NFP will introduce you to what NFP is, how it works, and ends with an overview of the 4 main categories of NFP methods—calendar based methods, mucus-only methods, symptothermal methods, and symptohormonal methods.

Our goal with this guide is to introduce you to your NFP options so you can make an informed decision about which method will suit you best.

About the Authors

This guide was written by the team of nurses who teach NFP at Vitae Fertility Education. We teach the Marquette Method of NFP, a symptohormonal method of Natural Family Planning which works by measuring hormone levels directly, using a fertility monitor.

We’re pretty committed to Marquette—together, we’ve taught more than 6000 couples how to use the method. We all use the Marquette Method, too.

So why did we create this guide?

We don’t believe there is one “best” method of NFP for all women, all the time. We’re healthcare professionals, committed to informed consent.

We never want people to choose Marquette without knowing about all the other options.

Team picture of the Marquette Method Instructors who teach with Vitae Fertility

Instructors on the Vitae Fertility Teaching Team (see full group)

Part 1:

How Effective is Natural Family Planning?

NFP is not “one thing.”

There are several modern methods of NFP, and they all work differently. There is no such thing as a “best” NFP method, since no one method is the perfect fit for all women, all the time.

Each NFP method has conducted its own effectiveness studies. Effectiveness rates for NFP methods vary, both between methods (some methods are more effective than others) and between studies (different studies have shown different effectiveness rates, even for the same method).

When used correctly and under the advice of a trained fertility educator NFP can be up to 99% effective in perfect use and 98% effective in typical use (Peragallo Urrutia et al., 2018).

Method effectiveness is the #1 concern of most people considering natural family planning. Rather than reproducing a chart of effectiveness rates, we’d like to direct you to the most reliable third-party research, because numbers without context don’t mean much.

Recommended reading on NFP/FABM effectiveness rates

Peragallo Urrutia, R., Polis, C. B., Jensen, E. T., Greene, M. E., Kennedy, E., & Stanford, J. B. (2018). Effectiveness of fertility awareness–based methods for pregnancy prevention: A systematic review. Obstetrics & Gynecology132(3), 591.

See also this interactive infographic which presents the results of the paper, including perfect use and typical use failure rate ranges by method.

But … Does it Work?

Feeling called to use natural family planning (NFP) to avoid pregnancy, but have serious questions about its effectiveness?

It’s OK to be skeptical.

The truth is, not all methods of NFP are equally effective for all women.

Louise Boychuk, founder of Vitae Fertility Education, explains it all in this plain-language, no-fluff guide to NFP effectiveness rates, and she gives advice on how to choose a method that’s going to be the most effective, for you.

How does Natural Family Planning Work?

Introducing … Your Hormone Cycle

NFP works because hormone levels fluctuate as the woman’s cycle progresses. These hormones will fluctuate in a predictable, cyclical pattern.

Women who track their hormone curves use this information to determine the “fertile window” in each cycle—the days on which is it possible to conceive.

In a typical cycle, follicle stimulating hormone (FSH) levels rise near the beginning of the cycle. Rising FSH levels will stimulate a follicle to begin developing an egg – this happens in the ovary. As the egg develops, the woman’s estrogen levels will begin to rise.

When the egg is fully developed, the woman’s estrogen levels will be nice and high. In response to elevated estrogen levels the body will have a luteinizing hormone (LH) surge. The LH surge will last 18-36 hours.

graph of the lh surge in a menstrual cycle, which occurs 12 to 24 hours before ovulation

This “LH surge” prompts ovulation—which is when an ovary releases a developed egg (ovum). The egg remains viable (able to be fertilized to create new life) for up to 24 hours. Women only ovulate once per cycle.

(Sometimes, like in the case of fraternal twins, more than one egg will be released in this ovulatory event.)

After ovulation, the empty follicle will begin to dissolve – this empty, dissolving follicle is called the corpus luteum. As the corpus luteum dissolves, it releases progesterone. The post-ovulatory rise in progesterone is a clear sign ovulation has occurred.

Each of these hormonal shifts—the estrogen rise, the LH surge, and the rise in progesterone after ovulation—cause the woman’s body to external exhibit measurable physical signs and symptoms.

These “fertile signs” show what’s happening internally. Tracking these fertile signs—in real time—is what NFP is all about.

It’s how modern NFP methods work.


What is the difference between Natural Family Planning (NFP) and Fertility Awareness Based Methods (FABMs)?

NFP and FABMs are pretty much the same thing.

When used to avoid pregnancy, both are “natural birth control” methods which work by identifying fertile days.

The main difference between NFP and FABMs is that FABMs allow couples to use contraception (such as condoms) during the fertile window.

NFP methods, in alignment with Catholic Church teaching against the use of contraceptives, instead prescribes abstinence during the fertile window.

How Does Natural Family Planning Work?

Learning the Signs of Fertility

1. Rising estrogen prompts cervical mucus production

As estrogen levels rise, the cervix begins to produce cervical mucus. (The cervix is the entryway to the uterus, at the top of the vaginal canal.)

While estrogen levels remain low, cervical mucus tends to be tacky, sticky, opaque and “scant” (not a lot of it).

As estrogen levels rise, a different kind of mucus—“peak type” cervical mucus—appears. Peak-type mucus is clear, stretchy, thin, and abundant. Peak mucus looks and feels a lot like egg whites, so it’s sometimes called “EWCM” for “egg white cervical mucus.”

graph explaining how the rise in estrogen at the beginning of the cycle changes cervical mucus. While estrogen levels remain low, cervical mucus is tacky, sticky, and opaque. When estrogen levels peak, it becomes stretchy, clear, and thin

2. LH surge prompts ovulation

LH surges in the lead up to ovulation—the surge happens about 18 to 24 hours before ovulation. Unlike estrogen, the LH surge does not exhibit any physical symptoms. You can only measure LH levels by doing a blood test or a urine test.

For NFP purposes, women who track their LH levels do so by using an LH test stick. The Clearblue Fertility Monitor test sticks and the Mira fertility monitor wands measure LH (and estrogen levels too). 

3. Rising progesterone prompts the temperature shift

After ovulation, the corpus luteum (which held the egg) begins to disintegrate and release progesterone. Progesterone’s role is to thin the endometrium and to make the endometrial lining more vascular, so that a fertilized egg can implant and begin to grow. Progesterone levels remain high until the end of the cycle.

The progesterone rise the women’s resting basal body temperature (BBT) to rise. This temperature shift is subtle but measurable.

To identify the day of this shift, women take BBT readings every morning and plot them on a chart. (You can also measure progesterone directly in urine using a Proov test stick or the Mira fertility monitor “confirm” wands.)

chart for NFP users showing how rising progesterone levels after ovulation prompt the BBT/temperature shift

Part 2:

Types of Natural Family Planning Methods

There are a lot of hormone fluctuations that happen in a woman’s body that lead to the development of the egg and follow ovulation, these hormone fluctuations can be used to measure or track to determine the fertile time in the woman’s cycle. Cervical mucus, BBT readings, cycle statistics, and urinary hormone testing are all possibilities. 

As we cover in our online intro to natural family planning class there are many different NFP methods to choose from.

Every NFP method is the same in that they are tracking the hormone fluctuations in the cycle. Every NFP method is a little different in which signs it tracks and how it identifies the fertile days. As such every NFP method will be different in how effective it is, and how many days are identified in the fertile window. 

Broadly speaking, there are 4 types of NFP methods:

  1. calendar based methods
  2. mucus-only methods
  3. symptothermal methods
  4. symptohormonal methods

Calendar-based methods

Calendar-based methods of NFP use the woman’s cycle history to predict the fertile window. All a woman needs to know is her cycle length—the number of days from “day 1” of one period to “day 1” of her next period.

Calendar-based methods can be quite effective for women who have regular cycles. They cannot be used effectively by women who have long cycles, short cycles, or irregular length cycles. Women in the transitional seasons of fertility (e.g. postpartum, post-hormonal contraception, or in perimenopause) also can’t use calendar-based methods.

Calendar rhythm methods of NFP include

  • The Standard Days Method (SDM)
  • The DOT app

Fun fact: Most “NFP apps” are calendar-based methods—the app records a cycle history (date your period started in previous cycles), applies some fancy algorithmic math, and predict when you’ll be fertile in this cycle.

marquette NFP breastfeeding protocol user manual

FAQ: Modern NFP vs. “The Rhythm Method”

What’s the difference between the rhythm method and modern methods of natural family planning?

The main difference between old-school “rhythm method” approaches and modern natural family planning is that modern NFP allows women to track their fertility in real time, day by day.

The rhythm method, by contrast, uses a set, pre-determined fertile window.

There’s a lot of variability in women’s cycles (both from woman to woman, and even for the same woman, from cycle to cycle).

Modern NFP methods are more effective than the rhythm method because this variability is accounted for.

Mucus-Only Methods of NFP

Cervical mucus is a useful indicator of fertility because it can identify the entirety of the fertile phase—the beginning, the end, and the peak. Mucus-only methods of NFP are also called single-indicator or single-index methods.
One benefit of mucus-only methods is that they are free to use. You don’t need to buy a thermometer or fertility monitor to use them. Because you track mucus every day, they are suitable for women who have longer, shorter, or irregular-length cycles.

Some women find mucus tracking too subjective or confusing, especially if they have mucus every day. Mucus needs to be tracked throughout the whole day and whole cycle—some women find this onerous.

Mucus tracking can be challenging in the transitional phases of a woman’s fertility, such as after giving birth, when coming off hormonal contraception, or during perimenopause.

Research has shown that the mucus symptoms are a less reliable indicator of hormone fluctuations for breastfeeding women than it is for regularly cycling women (Bouchard et al., 2018)

Mucus-only methods of NFP include:

  • Two Day Method
  • The Billings Ovulation Method (OM)
  • The Creighton Model FertilityCare System (CrMS)

Symptothermal methods of NFP

Symptothermal methods of NFP track more than one fertile sign concurrently. Like mucus-only methods, women who use symptothermal methods track their mucus daily (that’s the “sympto”). Unlike mucus methods, symptothermal methods also track temperatures daily, to identify the BBT shift (that’s the “thermal” part).

Some symptothermal methods also factor in the woman’s cycle history into their calculations, which can provide further certainty into the actual fertile days.

The big advantage of symptothermal methods is that they are not reliant on one sign. Sometimes sympotothermal method are called “double-check” or “cross-check” methods of NFP because they allow a woman to identify the days of fertility in more than one way. If all the fertile signs “agree” (all point towards fertility or all point towards infertlity) then a woman can be especially confident of the phase of fertility she is in. Some research has shown that double-check methods of NFP might be more effective than single-check methods (Freundl, 1999).

Unfortunately, adding in more fertile signs also means that there’s a chance that the signs don’t agree. Just to give one example, drinking alcohol can disrupt BBT readings and obscure the temperature shift in a cycle. Symptothermal methods are very effective, but they do have more “moving parts” to learn than some other methods.

It’s important to know that when a woman isn’t ovulating (perhaps because she’s nursing a baby) symptothermal methods essentially turn into mucus-only methods. The BBT shift only occurs after the first ovulation, which might not happen for months (Bouchard et al., 2013). 

Symptothermal methods of NFP Include:

  • Couple to Couple League International (CCLI)
  • Serena
  • Sensiplan Double Check
  • Symptopro

Symptohormonal methods of NFP

The Marquette Method of NFP, the method we teach here at Vitae Fertility, is a symptohormonal method.

We’re obviously biased, but like to think of symptohormonal methods as kind of like the swiss army knife of modern NFP.

The key difference between symptohormonal methods and other forms of NFP is that instead of tracking the symptoms of hormonal changes (cervical mucus and/or BBT), it tracks hormones directly, in a woman’s urine sample.

Urinary hormone testing is a lot like taking a pregnancy test, but instead of it telling you if you’re pregnant or not, it tells you whether you’re fertile or not.

And, like calendar-based methods and symptothermal methods, the Marquette Method also uses a woman’s cycle history as a part of the system.

The main advantage of the Marquette Method is it’s based off of an objective measure of fertility—it’s all very “black and white.”

Clearblue Fertility Monitors only ever give one of three results—low, high, or peak. Women don’t have to learn how to interpret the symptoms of fertility.

In fact, many of the women we teach tell us how much more confident they are while using the monitor, confident that they’re using the method correctly. Women who have tracked mucus for years find out they understand their mucus  types better they had the monitor providing an objective indication of when their estrogen rise and LH surge were occuring.

Another advantage of symptohormonal methods are that they’re a “custom fit” approach to NFP. Marquette is not just one set of instructions. Women can choose to track other fertile signs (including cervical mucus or BBT) alongside urinary testing.

The Marquette Method really shines during the transitional stages of a woman’s fertile life, like postpartum and perimenopause. In these cases, hormone levels can be tracked daily and aren’t affected by the presence or absence of cycles. 

The main disadvantage to symptohormonal methods is that you need supplies. To use the Marquette Method, women need to purchase a Clearblue fertility monitor and disposable, single-use test sticks. (This can be a significant barrier to some couples, so we have compiled a list of ways to save on Marquette method supplies here.)

It’s important to know that when a woman isn’t ovulating (perhaps because she’s nursing a baby) symptothermal methods essentially turn into mucus-only methods. The BBT shift only occurs after the first ovulation, which might not happen for months (Bouchard et al., 2013). 

Symptohormonal methods of NFP include:

  • The Marquette Method of NFP
  • FEMM Health (if used with LH testing)
  • Natural Cycles (if used with LH testing)

Part 3:

Why Do Catholics Use NFP?


Everyone has their own reason for using NFP.

Many couples use Natural Family Planning because they are Catholic. They use NFP because they want to live their married life in accordance with their body’s design.

Not all of our clients are Catholic, but most of them are! Most of the effectiveness research into NFP has been with Catholic couples. The Catholic Church has long taught that NFP is a licit way for husbands and wives to limit or space pregnancies, and the Marquette Method is one of the many NFP methods that are approved by the Church!

​What does the Church teach about NFP?

In the 1968 encyclical Humane Vitae, Pope Paul VI taught that “married people may then take advantage of the natural cycles immanent in the reproductive system and engage in marital intercourse only during those times that are infertile, thus controlling birth in a way which does not in the least offend the moral principles” (source)

St. John Paul II elaborated on this doctrine more fully in the Theology of the Body, a series of 129 lectures he gave during his Wednesday Audiences between 1979 and 1984.

Do you have to be Catholic to use NFP?

It’s not just Catholics that use Natural Family Planning, non-Catholic couples often use the same systems and just call the methods Fertility Awareness Based Methods (FABMs) or even just “natural birth control.” Couples from all walks of life turn to NFP/FABMs to manage their fertility in a natural, holistic way.

There are very practical reasons for choosing NFP, too. A growing number of couples turn to NFP because they find out that, for them, hormonal birth control comes along with unpleasant side effects such as mood disorders, headaches, nausea, weight gain, or decreased libido.

Many couples appreciate not needing to use condoms and choose to use NFP to deepen their intimacy.

Deciding to practice NFP—and choosing which method to use—is a very personal decision.

Whatever your reason for wanting to learn NFP, we would be glad to work with you at Vitae Fertility.


Peragallo Urrutia, R., Polis, C. B., Jensen, E. T., Greene, M. E., Kennedy, E., & Stanford, J. B. (2018). Effectiveness of fertility awareness–based methods for pregnancy prevention: A systematic review. Obstetrics & Gynecology132(3), 591.

Bouchard, T., Fehring, R. J., & Schneider, M. (2013). Efficacy of a new postpartum transition protocol for avoiding pregnancyJournal of the American Board of Family Medicine26(1), 35–44.

Bouchard T, Blackwell L, Brown S, Fehring R, Parenteau-Carreau S. Dissociation between Cervical Mucus and Urinary Hormones during the Postpartum Return of Fertility in Breastfeeding Women. The Linacre Quarterly. 2018;85(4):399-411. doi:10.1177/0024363918809698 

Freundl, European multicenter study of natural family planning (1989-1995): efficacy and drop-out. The European Natural Family Planning Study Groups. (1999). Advances in contraception : the official journal of the Society for the Advancement of Contraception15(1), 69–83.

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