How Effective Is the Billings Method?

What the research actually tells us about correct use, typical use, and why the numbers vary.

If you are considering the Billings Ovulation Method, one question matters pretty quickly:

Does it actually work?

The short answer is yes: Billings can be highly effective when it is correctly learned and consistently followed.

The longer answer is more useful.

Studies of Billings report very different pregnancy rates depending on the population being studied, the quality of instruction, how researchers define correct use, and what couples choose to do during days identified as potentially fertile.

That means there is no single honest number that tells the whole story.

So rather than giving you the most impressive statistic we can find, let's look at what the research actually shows.

What do the Billings studies show?

Two older studies are often cited in discussions of Billings effectiveness.

In a 1981 prospective study conducted across five countries, 725 couples entered a 13-cycle effectiveness phase after completing instruction in the method.

Researchers reported pregnancy rates of:

• 2.8 per 100 woman-years attributed to method failure
• 3.5 per 100 woman-years attributed to inaccurate application of the instructions
• and considerably more pregnancies when couples knowingly had intercourse during days the method identified as fertile.

A later study in Shanghai followed 688 couples using Billings. At 12 months, the reported cumulative unintended-pregnancy rate was 1.02 per 100 women.

Those numbers are encouraging.

But they are not the whole evidence base.

What does the broader research say?

A 2018 systematic review examined 53 prospective studies of fertility-awareness methods.

That review is useful because it looked not only at individual studies, but also at the quality of the evidence behind them.

Of the 53 studies, none were rated high quality for the review's effectiveness question. Twenty-one were considered moderate quality and 32 low quality.

Among the moderate-quality Billings studies, researchers found approximately:

• 1.1 to 3.4 pregnancies per 100 woman-years with correct use
• 10.5 to 33.6 pregnancies per 100 woman-years with typical use

That is a big range.

And it deserves to be shown rather than hidden.

The review also cautioned that differences among study populations make direct comparisons between fertility-awareness methods difficult.

So when someone gives you one exact "Billings failure rate," it is worth asking what kind of use, and which study, they are talking about.

Correct use and typical use are not the same thing

Nearly every method of postponing pregnancy performs differently under perfect or correct use than it does in everyday life.

Correct use asks:

What happens when the method is understood and followed as intended?

Typical use asks:

What happens among everyone using it in real life, including missed observations, misunderstandings and decisions that do not follow the method's guidance?

Billings has a particularly noticeable gap between those numbers because it requires active participation.

There is no device continuously doing the work for you.

You observe.

You interpret.

And if you are postponing pregnancy, you and your spouse decide how to respond to the fertile pattern.

That is both a strength of the method and a responsibility that comes with using it.

Does that mean typical-use pregnancies are just "user error"?

We would not describe them that way.

How easy or difficult a method is to follow is part of its real-world effectiveness.

People get sick.

Babies wake up.

Observations get missed.

Instructions can be misunderstood.

Couples can make different decisions than they originally intended.

Good effectiveness research needs to account for real life, not simply dismiss it.

At the same time, it is useful to distinguish a pregnancy that occurs while the method's rules were followed from one that occurs after intercourse on a day already recognized as potentially fertile.

Those are different questions.

The original WHO study specifically separated those outcomes, which helps explain why several different pregnancy rates can come from the same group of participants.

Why does good instruction matter?

Billings looks simple because it does not require many tools.

But simple does not mean automatic.

A woman is learning to recognize sensation at the vulva, her Basic Infertile Pattern, changes from that pattern, the developing fertile pattern and Peak.

Those distinctions become much clearer with practice.

A 2023 qualitative study of Billings users found that many women valued experienced instructors who could review charts, simplify terminology and help them interpret difficult seasons such as breastfeeding or PCOS.

The same study also found that the learning curve was real. Some women needed several months before they felt confident recognizing their patterns, and not every experience with an instructor was equally good.

That feels much closer to real life than saying Billings is effortless.

It is learnable. But it is something you learn.

How quickly can women learn it?

The original WHO teaching study included 869 women across five countries and a broad range of educational backgrounds.

During the first teaching cycle, 93% recorded an interpretable ovulatory mucus pattern. Eighty-eight percent ultimately completed the teaching phase successfully.

That tells us something important:

Women can learn to recognize the pattern.

But it does not mean every woman becomes fully confident after one cycle.

Confidence tends to grow as she sees her own pattern repeat.

Is Billings as effective as the pill?

This is where comparisons get messy.

It is tempting to put two percentages beside each other and declare a winner.

But studies of Billings and studies of hormonal contraception are conducted in different populations, under different conditions and using different research designs.

Current CDC guidance estimates that about 7 out of 100 users of combined hormonal contraceptives become pregnant during the first year of typical use. For IUDs, typical-use pregnancy rates are below 1 per 100 users.

ACOG gives a broad estimate for fertility-awareness methods as a category: fewer than 1 to 5 pregnancies per 100 women with perfect use and approximately 12 to 24 with typical use. But that category includes several very different methods.

Billings-specific research shows strong correct-use results, but the evidence does not justify saying simply that Billings and the pill are equally effective.

We would rather give you the nuance than the marketing line.

Then where does the "25% failure rate" come from?

You may have seen fertility-awareness methods described as having a failure rate around 24 or 25 percent.

Part of the problem is that clinical resources often group very different fertility-awareness approaches into one category.

Calendar methods, cervical-mucus methods, symptothermal methods and other approaches do not all perform identically.

But it would also be misleading to say that 25 percent has nothing to do with Billings.

In the systematic review, typical-use Billings results varied considerably, with some studies reporting pregnancy rates above that level.

The better takeaway is:

Do not judge a specific method by one broad fertility-awareness statistic, and do not judge it by its best study alone, either.

Look at the whole evidence.

What if you are trying to conceive?

The same observations can also help a couple recognize when conception is most likely.

Cervical mucus changes in response to the hormonal events leading toward ovulation, and research supports cervical-mucus monitoring as a useful way of identifying days with a higher probability of conception.

Billings does not become a different method when your intention changes.

You keep observing the same body.

What changes is what you do with the information.

That continuity is one of the things we love about the method.

What about irregular cycles, postpartum or breastfeeding?

Billings is not built around the assumption that ovulation happens on Day 14.

It responds to the pattern a woman observes in the cycle she is actually having.

That makes the underlying approach particularly useful during seasons when calendar predictions become less meaningful.

Those seasons can also make chart interpretation more complex.

The 2023 study of Billings users specifically found that women breastfeeding or living with PCOS sometimes found their patterns harder to interpret and valued additional instructor support.

So "Billings works with irregular cycles" should not mean "irregular cycles are always easy to chart."

Sometimes they are precisely when good instruction matters most.

What does Corvia have to do with effectiveness?

Corvia makes Billings easier to learn, record and see.

It does not make the biological method more effective by itself.

That distinction matters.

Corvia can help you remember to observe, keep your chart organized, look across previous cycles, share your chart with your spouse or instructor, and learn the principles behind what you are seeing.

But Corvia does not replace understanding the method.

The woman still makes the observation.

The pattern still belongs to her.

And if a couple is relying on Billings to postpone pregnancy, learning the method correctly matters.

That is why Corvia includes Billings education rather than simply handing you a fertility prediction.

So, how effective is Billings?

The strongest answer is not a single percentage.

Research suggests that correctly learned and consistently followed Billings can have low pregnancy rates, with moderate-quality studies reporting roughly 1 to 3 pregnancies per 100 woman-years with correct use.

Real-world outcomes vary substantially more.

Both facts matter.

And perhaps that is the most important thing to understand before choosing the method:

Billings does not promise to manage fertility for you.

It teaches you to recognize fertility yourself.

For some women and couples, that responsibility is exactly what they are looking for.

Frequently asked questions

What is the failure rate of natural family planning?

It depends entirely on which method and which study. Well-taught Billings Ovulation Method has a method-related failure rate of about 2.8 per 100 woman-years, per the WHO Five-Country Trial. Calendar-based methods and self-taught mucus methods have significantly higher failure rates. Any single "NFP failure rate" number that lumps them together is misleading.

Can you get pregnant using the Billings Method?

Yes, in about 1 to 3 out of 100 women per year with correct use, and more often with inconsistent use. BOM is not a barrier and does not prevent conception. It provides the information a couple needs to make their own decision about intercourse during the fertile phase.

Is BOM approved by the FDA as contraception?

No. The Billings Ovulation Method is a body of knowledge and observation, not a medical device or drug, so it is not FDA-regulated. Digital tools that offer fertility-status outputs based on BOM data are regulated separately. Corvia is a charting and education tool, not a contraceptive device.

How long does it take to learn the Billings Method?

Most women can identify their fertile phase within the first charting cycle. The WHO teaching-phase trial (PMID 7021189) found that 93 percent of women across five countries recognized the fertile phase in their first cycle of observation. Confidence and full pattern recognition typically build over three to six cycles with instructor support.

Does BOM work if my cycles are irregular?

Yes. BOM is not calendar-based, which is exactly why it works when cycles are irregular. It responds to what your body is doing in the current cycle, not to what it did in previous cycles. This is one of its structural advantages over methods that assume regularity.