Rhythm method birth control

The Truth About the Rhythm Method

People have wanted and needed to prevent pregnancy for thousands of years. Before the birth control pill and condoms came along, couples had to figure out their fertile days each month, and avoid sex during those times. Today, that’s known as periodic abstinence, also called the rhythm method.

How the Rhythm Method Works

Abstinence means completely avoiding sex — the only 100-percent effective way to prevent pregnancy. But many couples practice periodic abstinence as birth control, meaning they abstain from sex during the time when the woman is fertile.

“What we know about pregnancy is that there is a very short time period in which an egg can be fertilized,” says Jennifer A. Shuford, MD, MPH, director of applied science at the Medical Institute for Sexual Health in Austin, Texas. “There are times of the month then when it should be impossible to get pregnant if the woman has not ovulated and won’t within five to seven days of intercourse. So the trick comes knowing exactly when you’re going to ovulate.”

Related: Pregnancy Dos and Don’ts

For the rhythm method to be effective, not only does a couple need to practice abstinence when the woman ovulates, they have to continue to do so for several days before and after. Because even though eggs don’t stay in the reproductive tract very long, sperm do.

“There are one to two days where that egg is able to be fertilized, but sperm can live for five to seven days,” says Dr. Shuford. So if sperm is sitting in the reproductive tract waiting for that egg to come down, she says, a woman can still get pregnant even if she had sex several days before ovulation.

Is the Rhythm Method Effective?

When done correctly, the rhythm method can be very effective. If egg and sperm can’t meet to fertilize, there is no chance of pregnancy. But that doesn’t mean it’s easy to do.

“Most women cannot peg ovulation precisely enough to know when the safe times to have sex are. It can be an effective form of birth control, it’s just that you have to leave a lot of buffer within your month to avoid getting pregnant,” says Shuford.

On average, the rhythm method is between 80 and 87 percent effective at preventing pregnancy, mostly because abstinence has to be practiced on more than just one or two days — it can take up to 10 days without sex to prevent pregnancy.

Related: 10 Healthy Ways to Handle PMS

For many women, it’s just too difficult to predict when they ovulate because ovulation doesn’t occur on the same schedule every month.

The rhythm method, says Shuford, is most appropriate for women who have extremely regular menstrual cycles, and ovulate regularly at the same time each month.

Rhythm Method: Recognizing Ovulation

The only way to make the rhythm method effective is to be able to recognize, as a woman, when you are ovulating. Here are some ways to tell that ovulation is near or occurring:

  • Look for a rise in body temperature. You have to take your temperature every morning in order to notice the 0.4 to 0.8 degree F rise in temperature, which can indicate ovulation. Temperature should be measured with a basal thermometer (which can detect very slight temperature increases) first thing in the morning, even before you get out of bed, and written down or charted. Look for a pattern of a slight decrease just before ovulation, followed by an increase in your body temperature. Once the temperature goes up, ovulation has already occurred. Basal thermometers are available in many pharmacies.
  • Check your cervical mucus. Around ovulation, your cervical mucus increases and changes texture. You can easily see and feel this discharge — it’s clear in color, wet, and stretches easily. When you notice the mucus giving the most stretch and appearing colorless and wet, that signals that you’re ovulating that day.
  • Use a calendar. Once you’ve learned how to tell when you’re ovulating, mark those dates on a calendar. Track it over a period of time and look for a pattern to see how regular your cycle and ovulation days are. If you ovulate regularly, you should be able to effectively prevent pregnancy by abstaining from sex for at least five days before and three days after ovulation. Online tools, such as the ovulation calculator on our partner site What to Expect, are also useful.
  • Ovulation kits. Another good way to tell if you are ovulating is to purchase ovulation test strips or the more expensive kits, which work like a home pregnancy test. The kit contains a monitor and disposable urine test strips. It works by measuring the amount of luteinizing hormone in your urine, which is a good predictor of ovulation. The monitors in the kits can be pretty pricey — some are more than $100. Ovulation kits are used most often by women who are trying to get pregnant, rather than those trying to prevent pregnancy, but they are helpful either way.

Women aren’t fertile every day of the month, so there are plenty of days when it’s just impossible to get pregnant. The fact is that using the rhythm method still poses a risk that you’ll get pregnant, as does any method of birth control. Which birth control method your most comfortable with depends on the level of risk that you and your partner are willing to take.

What are Fertility Awareness Methods?

Fertility awareness methods (FAMs) are ways to track your ovulation so you can prevent pregnancy. FAMs are also called “natural family planning” and “the rhythm method.”

X in a circle

Want to learn how to track your fertility?

Find a Health Center A right arrow in a circle

What are the different kinds of FAMs?

Fertility awareness methods help you track your menstrual cycle so you’ll know when your ovaries release an egg every month (this is called ovulation).

The days near ovulation are your fertile days — when you’re most likely to get pregnant. So people use FAMs to prevent pregnancy by avoiding sex or using another birth control method (like condoms) on those “unsafe,” fertile days.

There are a few different FAMs that help you track your fertility signs. You can use 1 or more of these methods to predict when you’ll ovulate:

  • The Temperature Method: you take your temperature in the morning every day before you get out of bed.

  • The Cervical Mucus Method: you check your cervical mucus (vaginal discharge) every day.

  • The Calendar Method: you chart your menstrual cycle on a calendar.

It’s most effective to combine all 3 of these methods. When used together, they’re called the symptothermal method.

The Standard Days Method is a variation on the calendar method. You track your menstrual cycle for several months to figure out if your cycle is always between 26 and 32 days long — you can’t use this method if it’s longer or shorter. Once you’ve established that your cycle is in the right range, you use another form of birth control (or don’t have vaginal sex) on days 8-19, which is when you’re fertile.

How effective are fertility awareness methods?

FAMs are about 76-88% effective: that means 12-24 out of 100 couples who use FAMs will get pregnant each year, depending on which method(s) are used. If you use multiple FAMs together, they work even better.

The better you are about using FAMs the right way — tracking your fertility signs daily and avoiding sex or using birth control on “unsafe” days — the more effective they’ll be. But there’s a chance that you’ll still get pregnant, even if you always use them perfectly.

Fertility awareness methods don’t work as well as other types of birth control because they can be difficult to use. Want a more effective way to prevent pregnancy? Check out IUDs and implants, or take this quiz to find the birth control method that’s best for you.

How can I make FAMs more effective?

Like all birth control methods, FAMs are more effective when you use them as perfectly as possible. How well FAMs work also depends on both partners, so it’s important that each of you is supportive and learns how to use the methods.

FAMs are most effective when:

  • you work with a nurse, doctor, or counselor who knows FAMs well to learn how to use them correctly

  • you have the time and discipline to check your fertility signs and chart your cycle every day

  • you and your partner don’t mind avoiding vaginal sex or using another kind of birth control around your fertile days

The best way to use FAMs is to combine the temperature, cervical mucus, and calendar methods. Each of these methods relies on different signs to predict your fertile days, so using them together gives you the best picture of your fertility and makes FAMs more accurate. For example, keeping track of your cervical mucus pattern can be useful if your temperature chart gets messed up because you’re sick or stressed. And using more than 1 method may help you narrow down your fertile days, so you will more safe days each month.

You can keep track of your mucus, days, and temperatures on a fertility awareness method chart like this one.

What do I need to know about my menstrual cycle and fertility?

In order to use FAMs, you’ve got to learn a lot about your menstrual cycle. You have to know when you’re ovulating and fertile, and when it’s safe for you to have sex without risking pregnancy.

In order for pregnancy to happen, a sperm cell must join with your egg (this is called fertilization). During your menstrual cycle, there are certain days when it’s possible for sperm to fertilize an egg and cause a pregnancy — these are your fertile days.

Each month, your ovary releases an egg into your fallopian tube (this is called ovulation). Your egg is in your fallopian tube for about 12-24 hours. Sperm can hang out in your uterus and fallopian tube for up to 6 days after sex. If a sperm cell does join up with your egg in the tube, the fertilized egg travels from your fallopian tube to your uterus (womb) and can attach to the uterine wall, which starts a pregnancy. If your egg doesn’t get fertilized, it dissolves and you eventually get your period.

Since an egg lives about a day after ovulation and sperm live about 6 days after sex, you’re basically fertile for around 7 days of every menstrual cycle: the 5 days before you ovulate, and the day you ovulate. You can also get pregnant a day or 2 after ovulation, but it’s less likely.

More questions from patients:

What is natural family planning or natural contraception? How do natural birth control methods work?

“Natural” family planning is when you track your menstrual cycle and ovulation to estimate what days you’re fertile, and then avoid unprotected penis-in-vagina sex on those days to prevent pregnancy.

There are a few ways to monitor your fertility for birth control — they’re called Fertility Awareness Methods (FAMs for short). Every day you take your temperature, monitor your cervical mucus, and/or chart your menstrual cycle to track your fertility signs. Using all 3 methods together works best, and it’s important to make sure you’re doing them every day.

FAMs are a great way to learn about your body, and they can be really effective if you have regular cycles and stay on top of tracking your fertility signs perfectly. Many people who use FAMs also like that there aren’t any side effects. But FAMs can also be difficult to use correctly, and won’t work well if you have an irregular menstrual cycle.

Sometimes when people talk about “natural” birth control, they mean a birth control method that doesn’t have hormones. If FAMs aren’t your thing but you want a super effective birth control method without hormones, check out the copper IUD. Condoms are another way to prevent pregnancy without hormones, with a great perk of also protecting against STDs. (Some people who use FAMs also use condoms on their fertile days.)

Was this page helpful?

  • Yes
  • No

Help us improve – how could this information be more helpful?

How did this information help you?

You’re the best! Thanks for your feedback. Thanks for your feedback.

Calculating the safe period

Many shared Leo Latz’s faith in the science behind the Ogino-Knaus findings. But to apply them to birth control is not always so simple, nor straightforward. Calculating the time of ovulation can still be tricky. It varies from woman to woman, and a woman can ovulate at a different time each month. Stress, illness, or interruptions in normal routine can also alter a woman’s cycle. Despite these uncertainties, the Ogino-Knaus method caught on, as evidenced by the proliferation of rhythm method calculators after 1930. Companies produced graphs, wheels, calendars, and slide rules, which cost from 10¢ to $5.

Only an engineer could make it work:
Gilmore Tilbrook and the “Rythmeter”

The “Rythmeter” ranks as one of the most intriguing devices for calculating the time of ovulation and the fertile and infertile periods of the menstrual cycle. Tilbrook, a consulting engineer, took on the challenge of making such a calculator. He recalled its genesis years later: …in 1930, on a visit at Graz, Austria, Dr. Knaus explained his conclusions regarding the exact time of ovulation of a human female. convinced of the importance of this theory – – especially to those of the Catholic Faith. A doctor friend exclaimed: “Tilbrook, you are an engineer – – Why can’t you work out a simple, foolproof calculator for the accurate application of the Rhythm?” Tillbrook conferred with leading medical experts on “Nature’s Rhythm Method,” including Leo Latz, Thurston S. Welton, C. G. Hartman, and Robert Latou Dickinson. The “Rythmeter” was an ingenious calculator, but even Tilbrook cautioned women not to use it without having a record of at least nine months of past menstrual cycles.

Roman Catholics and Rhythm

Among Roman Catholics, the rhythm method got a mixed response. Men and women anxious to limit their families saw it as a possible salvation. But Cardinal Hayes of New York cautioned, “Instead of being freely taught and commended, it (rhythm) is rather to be tolerated as an extreme remedy or means of preventing sin.” The Catholic Medical Guardian reported in 1935 that “the calculation of the ‘sterile period’ is never easy and in many cases appears to be impossible.” Advertisements in Catholic magazines for books and pamphlets on the rhythm method declined after 1934. Interest yet remained, and in 1951 Pope Pius XII sanctioned the rhythm method as a “natural” method of regulating procreation. In 1955 over 65% of Catholic women surveyed said they used Rhythm.

From Rhythm Method to Natural Family Planning

The Rhythm Method became even more popular when used in conjunction with new ways to determine the timing of ovulation. By measuring and recording body temperature, one can detect small changes, indicating that ovulation has occurred. This finding dates to research by Mary Putnam Jacobi in 1876 and was confirmed by T. H. Van de Velde in 1904. Van de Velde charted body temperature over a month and noted that the lowest basal body temperature, taken when one wakes in the morning, coincided with ovulation. This finding was applied to birth control in 1960 by Wilhlem Hillebrand, a German Catholic priest. Proponents of a natural form of birth control also gauged the timing of ovulation by noting changes in cervical mucus. This approach became knows as the Ovulation Method, or Billings Method, advanced by John and Eveyln Billings in 1964. The Sympto-Thermal Method of the late 1970s combined rhythm, temperature, and mucus signs.

The Billings Ovulation Method.

In 1953 Drs. John and Evelyn Billings of Melbourne, Australia, began work on a method of natural family planning based upon observed changes of cervical mucus during the monthly menstrual cycle. Those changes could be used to determine the time of ovulation and hence a woman’s period of fertility. The Billings’ interest stemmed from concern over the unreliability of Rhythm method. Negative side effects of the Pill added to their concerns after 1960. They collaborated with endocrinologist James B. Brown to further study the relationship between cervical mucus and fertility, specifically to measure the hormonal patterns of women. In 1964 John Billings outlined his work in The ovulation method; the avoidance of pregnancy in medical practice, by a technique which is safe, reliable and morally acceptable. In the ensuing decades, before his death in 2007, he and his collaborators championed the method worldwide. The World Health Organization sanctioned their efforts by terming it the Billings Ovulation Method.

The Standard Days Method

A new development in calendar-based methods occurred in 1999, when Georgetown University introduced the Standard Days Method. The Standard Days Method is promoted in conjunction with a product called CycleBeads, a ring of colored beads which are meant to help the user keep track of her fertile and non-fertile days. One concern related to the use of calendar-based or safe period methods is their relatively high failure rate, compared to other birth control methods. Even when used flawlessly, calendar-based methods, especially the rhythm method, result in a high pregnancy rate.

For years the birth control methods collectively known as periodic abstinence have been jokingly referred to as “Vatican roulette,” a nod to the fact that these techniques are both Vatican approved and quite likely to end in pregnancy. (The World Health Organization reports that on average, women practicing periodic abstinence for a year have a one in four chance of becoming pregnant.)

A new German study, however, has found that, when practiced correctly, a method of periodic abstinence known as the sympto-thermal method (STM) leads to an unintended pregnancy rate of only 0.6 percent annually. This rate is comparable with that of unintended pregnancies in women who use birth control pills, the most popular method of contraception in the U.S.

For the sympto-thermal method to work, women must keep track of three things: their core body temperature, the fertile days of their cycle as measured by a calendar, and their cervical secretions. Using this information, women are able to abstain from sex during their fertile period, which includes several days prior to and after the day of ovulation. According to lead study author Petra Frank-Herrmann, a fertility researcher at the University of Heidelberg in Germany, STM is more effective than the other so-called periodic abstinence methods because it uses more than one type of information to predict the dates of a woman’s fertile period.

As effective as STM can be, experts say it is not right for everyone. Whereas the method is cheap (read: free) and appeals to women who want a natural birth control method, it requires a strong commitment on the part of both partners.

“You really can’t extrapolate from this paper,” says David Grimes, an obstetrician-gynecologist and vice president of biomedical affairs at the nonprofit public health organization Family Health International. “Naive readers see these results, and they think is the greatest thing since laptop computers. The researchers on this paper went back and cherry-picked this data from an ongoing study from the past 20 years. They chose the users who were the best users for this method.”

Hilda Hutcherson, an ob-gyn and co-director of the New York Center for Women’s Sexual Health at New York-Presbyterian Hospital/Columbia University Medical Center, found that her patients often stop using periodic abstinence methods after only a few months. “It’s difficult to abstain from sex for two out of four weeks,” she says. “That means half the month you can’t have sex. That’s very difficult for young couples.” (It’s worth noting that STM actually requires only 7-10 days of abstinence, but related methods of birth control still practiced in the U.S. do require up to two weeks of abstinence every month.)

Grimes of Family Health International believes that studies of periodic abstinence are often motivated in part by religious beliefs. “Many of the authors of these studies have religious orientations,” he says, “and that clouds the motivations.” Some 74 percent of the women who participated in Frank-Herrmann’s study, which will be published in the journal Human Reproduction, listed their religion as Roman Catholic, a faith for which this is the only church sanctioned method of family planning.

But Suzanne Parenteau-Carreau, a researcher and an advisor at Serena, a Canadian volunteer organization devoted to teaching couples how to practice the method, disagrees. She says that although religion was the early impetus, couples who practice STM are now seeking “natural” birth control.

“Now it’s more and more from a natural motivation; to be closer to nature,” she says. “We often say it’s people who like camping, bicycling, outdoor exercise—people who want healthy food and healthy natural family planning.”

But that notion irks Grimes, who insists it is misleading. “I chafe at the term ‘natural family planning,'” he says. “For many couples this is highly unnatural. ‘Natural’ is methods that you don’t have to think about, that allow you to be spontaneous…. STM is very unpopular, hard to use, and has a poor success rate in average couples. Most people aren’t willing to put up with it.”

Frank-Herrmann acknowledges that one U.S. study conducted in 1980 in Los Angeles had a 90 percent dropout rate after less than two years.

But Grimes concedes that STM has its advantages, chief among them that “it is cheap, safe and approved by the Roman Catholic Church…. It is a reasonable part of the mix of contraceptive methods, it’s just that for most people it’s not an acceptable method.”

Whether or not this method will ever gain ground on other contraceptive methods—the most recent data available indicate that less than 1 percent of women who use birth control in the U.S. use any method of periodic abstinence—all observers agreed that STM can only work for couples who stick to the plan 100 percent.

“It’s not for everybody,” Frank-Herrmann notes, “but there is a group of women who are interested in this method, and I think we should offer it to them.”

The bottom line: all contraceptive methods have their drawbacks, including the potential of passing along the HIV virus and sexually transmitted diseases best prevented by condoms. Ultimately, Grimes says, “the best method for a couple to use is whatever they want. It’s counterproductive to try to steer people to one thing or another.”


The range of birth control choices may have become narrower for couples that believe the sanctity of life begins when sperm meets egg. The rhythm method, a philosopher claims, may compromise millions of embryos.

“Even a policy of practising condom usage and having an abortion in case of failure would cause less embryonic deaths than the rhythm method,” writes Luc Bovens, of the London School of Economics, in the Journal of Medical Ethics.

With other methods of contraception banned by the Catholic church, the rhythm method has been one of the few options available to millions.

In using the rhythm method, couples avoid pregnancy by refraining from sex during a woman’s fertile period. Perfect adherents claim it is over 90% effective – i.e. one couple in 10 will conceive in an average year. But, typically speaking, effectiveness is estimated at closer to 75%.

Now Bovens suggests that for those concerned about embryo loss, the rhythm method may be a bad idea. He argues that, because couples are having sex on the fringes of the fertile period, they are more likely to conceive embryos that are incapable of surviving.

Fertile window

As many as 50% of conceptions may not survive long enough even to disrupt menstruation, Bovens says. It is reasonable to assume then, he adds, that embryos created from sperm that has been sitting for days within the female’s reproductive tract before ovulation may be disadvantaged.

The situation is similar, he suggests, for eggs that have been waiting around for sperm to arrive. These are the only two likely scenarios where fertilisation might occur using the rhythm method, he points out.

These embryos may then face a less-than-ideal uterine lining, he points out, since the uterus is not as receptive outside of the most fertile period.

Bovens calculates that, if the rhythm method is 90% effective, and if conceptions outside the fertile period are about twice as likely to fail as to survive, then “millions of rhythm method cycles per year globally depend for their success on massive embryonic death”.

Pill under fire

Other birth control methods also fail the test in terms of preventing embryo death. The morning-after-pill, for instance, affects the uterine lining, so will prevent an embryo from implanting in the uterine wall.

Even the birth control pill has recently come under fire, since one of the ways it prevents pregnancy is by thinning the uterine lining, again making implantation unlikely.

Randy Alcorn, a pro-lifer and Christian minister in Gresham, Oregon, US, recently stated that “even an infinitesimally low portion – say, one hundredth of 1% – of 780 million pill cycles per year globally could represent tens of thousands of unborn children lost to this form of chemical abortion”.

Fertile fringes

“If you’re concerned about embryonic death,” Bovens says, “you’ve got to be consistent here and give up the rhythm method.”

Roger Gosden, at the Center for Reproductive Medicine and Infertility in New York, US, says: “It’s quite plausible that more abnormal embryos are conceived at the limits of sperm – and especially egg – viability,” he says, “and that these are more frequent in women practising rhythm contraception than those having unprotected intercourse at random stages of the menstrual cycle.”

He recalls that at least one study found that Roman Catholics had higher rates of miscarriage, presumably, he says, due to aged gametes. “Actually confirming this is not easy, though,” he admits.

Paul Tully, general secretary for the Society for the Protection of Unborn Children in London, UK, says this may cause concern to users of natural family planning. “It may lead to adjustment in the way they use it,” he says. “But I don’t think it will undermine the whole technique.”

Journal reference: Journal of Medical Ethics (vol 32, p 355).

Can The Rhythm Method Really Keep You From Getting Pregnant?

In this week’s Sex IDK column, Emma McGowan, certified sex educator and writer, answers your questions about the rhythm method.

Q: I want to know more about the rhythm method and non-hormonal contraception choices that are effective with low side effects.

The rhythm method, which is also sometimes called the “family planning method, the “calendar method,” or the “fertility awareness method,” is very likely the oldest birth control method humans have. Before there was the Pill, before there were condoms, before people were even using herbs to control conception, I’d be willing to bet that there were people who figured out that if you only had sex at certain times of the month, you wouldn’t get pregnant. Which makes it kind of surprising that so few young people know about this birth control method today!

One potential reason people don’t use this method as much today is because there are much more effective forms of birth control out there now. (Not to mention the fact that the rhythm method doesn’t protect against STIs.) We’ll get into how effective the rhythm method actually is, but I’m a firm believer in giving people more information about their reproductive choices, rather than less, especially if it means people with uteruses are better able to control their own bodies and futures.

So let’s talk about the rhythm method — what it is, what it isn’t, how people can best use it to track their fertility — as well as a couple of other non-hormonal birth control methods that can be used either in conjunction with or instead of the rhythm method.

Andrew Zaeh/Bustle

What Is The Rhythm Method?

The rhythm method is a birth control method that works by tracking your menstrual cycle so that you know when during the month you’re fertile, aka when you’re ovulating (about 14 days, give or take, after you start the blood part of your cycle). It can be used to either prevent pregnancy, or for people who are trying to get pregnant to know when sex will most likely result in fertilization.

While you might have been told at some point (most likely in sex ed) that you can get pregnant at any time of the month, the reality is that people with uteruses are fertile for about 12 to 24 hours, midway through their cycle. That’s it! Just a day!

But don’t think that this means you can have unprotected sex any other time except those 12 to 24 hours and not get pregnant. Turns out, sperm are tricky little buggers. They can live inside the vagina and the rest of the reproductive tract for up to around six days. Let’s take a look at why that’s important.

How Effective Is The Rhythm Method?

Before we get into anything, it has to be said: the rhythm method is not super effective. According to Planned Parenthood, it’s 76 to 88 percent effective to use one fertility awareness method by itself. That means 12 to 24 out of 100 couples who use only the rhythm method for birth control will get pregnant within a year. As you’re about to read, it can be really difficult to get all the info you need to practice this method perfectly. But, like all birth control methods, it’s more effective when combined with other forms of protection.

Andrew Zaeh/Bustle

How Are The Menstrual Cycle And Fertility Related?

During approximately a month-long time period, the bodies of people with uteruses who aren’t on hormonal birth control go through hormonal changes that determine what’s going on in those uteruses. The cycle begins on the first day of your period and lasts from 28 to 34 days, generally. For the first week — including the days you’re bleeding — it is extremely unlikely that you will get pregnant if you have unprotected sex, but it’s not impossible.

There is the very slight possibility of getting pregnant during that time, but really only if you have a super short cycle, like two or three weeks instead of four or five, and have penis-in-vagina sex toward the end of your period. If that’s the case, then you could theoretically still have live sperm inside your reproductive tract when you ovulate. (It also means you should see a doctor, because a cycle that short could mean there’s a health issue.) But if you have a four to five week cycle, as most people do, then having penis-in-vagina sex that first week doesn’t present a real risk of pregnancy.

During the second week of your cycle, it’s important to remember that sperm can live up to six days in the reproductive tract — in theory, long enough to fertilize an egg during ovulation. Just to be safe, it’s recommended that people who aren’t trying to get pregnant either refrain from sex or use a backup method during the full second week — meaning seven days — of their cycle.

Ovulation happens 14 days before your period starts. (So for people with 28-day cycles, that means day 14. For people with 34 day cycles, it’s day 20. You get it.) During ovulation, an egg busts out of the wall of the ovary and starts traveling down the fallopian tube, which connects your ovary to your uterus. It usually takes about a day for it to make that journey. That’s the time in which you can get pregnant, if live sperm makes it up there.

After that, if the egg isn’t fertilized, it dissolves once it hits your uterus — and the hormonal process that triggers your period in two weeks starts. If it is fertilized, it hangs out in the fallopian tube for a couple more days, and then implants in the wall of the uterus, where it starts growing into a fetus. But if it isn’t fertilized, it’s very unlikely that you would get pregnant in the last two weeks of your cycle. Once again, not impossible — you could theoretically ovulate a second time, or you could miscalculate the timing of ovulation — but very unlikely. And then, of course, the whole thing starts over again when your period starts.

Ashley Batz/Bustle

How Do You Track Your Cycle?

A strong understanding of your menstrual cycle is necessary in order to track it and use the rhythm method. So how do you do that? First, you have to figure out when you ovulate — which means you have to figure out how long your cycle is. In order to get a good understanding, Mayo Clinics recommends you observe your cycle for six to 12 months and track how long it is each month. This allows you to see whether or not your cycle is regular (which is important, because if it’s not regular, then this method is not going to be as effective for you) and also when you ovulate, on average.

Back in the day, people had to write down their cycles on a calendar or in a notebook to track them. Obviously that’s still an option, but there are also a ton of apps out there now that help you track your fertility. They’ll usually tell you which days in your cycle you’re fertile, so you can either avoid sex or use a backup method if you’re trying not to get pregnant, or have a bunch of sex if you are trying to get pregnant.

There are some questions about how fertility apps use and potentially sell your data, so it’s worth doing some research into that (and deciding how much data sharing you’re okay with) before starting to use one. If you’re not into the idea of being tracked while you’re tracking your cycle, a spreadsheet or a calendar works almost as well.

There are two other ways you can track ovulation. One is by taking your temperature every single day before getting out of bed, either with a thermometer or — if you want to be high tech about it — with a fertility tracking device and app. After you ovulate, your body temperature rises by a couple of degrees. Once that happens, the next couple of days are the fertile period. After three days at that temperature, you’re no longer fertile.

Another way to way to track ovulation is by tracking your cervical mucus and recording its consistency and color every day. Your cervical mucus changes throughout your cycle, so keeping track of it can help you figure out what part of your cycle you’re in. If you’re choosing either the temperature method or the cervical mucus method, it’s a really good idea to talk about it with a health care provider who can explain exactly what to do and how to do it, as well as what to look for.

Andrew Zaeh/Bustle

What Are Some Other Non-Hormonal Birth Control Methods?

If you’re trying not to get pregnant, then using the rhythm method on its own isn’t a great idea. (If you’re cool with maybe getting pregnant, however, it could be a good option!) There’s a lot of room for user error and, as I outlined above, the numbers really aren’t with you.

But if you use the rhythm method with another form of birth control, your chances of not getting pregnant rise significantly. These non-hormonal birth control methods can be used in conjunction with the rhythm method to help prevent pregnancy.


Any regular reader of Sex IDK knows that I am all about condoms. For pregnancy prevention, they’re 98 percent effective with perfect use and 85 percent effective with regular use. They’re also one of the few forms of brith control that people with penises get to be responsible for and they’re super effective against many STIs, including HIV.


For people who are sure that they don’t want to have kids, sterilization is a great option. In people with penises, the process is quick — and their partners never have to worry about birth control again. For people with uteruses, the process takes a bit longer and usually costs more.


Withdrawal — also known as “pulling out” — gets a bad rep because it’s another form of birth control that’s not very effective when you look at regular use. But when done perfectly, it can actually be super effective — only four in 100 couples using the pull out method perfectly will get pregnant within a year.

The problem is, it’s hard to do perfectly. Pulling out before ejaculation and making sure no ejaculate (aka cum) gets on the vulva or in the vagina can be really tricky — it’s not exactly a moment when most people are in control. So use this method with caution and maybe double up with condoms on fertile days.

Diaphragms and cervical caps

Diaphragms are a barrier method that used to be really popular, but as more effective contraceptives like the Pill and IUDs came on to the market, they fell out of popularity. But that doesn’t mean they’re not an option, especially when used in combination with the rhythm method.

A diaphragm is a shallow silicone cup that you slather with spermicide, fold up, and insert into the vagina so that it sits behind the pubic bone and over the cervix. When placed properly, the diaphragm blocks the entrance to the cervix and if any sperm sneak around it, the spermicide is there to zap them. Cervical caps are similar, but smaller. Both devices require a visit to the doctor so you can be fitted, shown how to use it, and get a prescription. With typical use, 12 out of 100 women who use a diaphragm may get pregnant within a year. For cervical caps, the number is a little higher: 17 to 23 out of 100 women.

So, is the rhythm method a good choice for pregnancy prevention? The answer to that question is the same as it is for any birth control method: It’s up to you to decide. Do your research, be honest with yourself about your habits, sexual and otherwise, and choose the method — or methods — that you can get behind. Remember, as with all things sex-related, it’s your body and your choice.

Read more from Bustle’s ‘Sex IDK’ column:

  • Can Antibiotics Make Your Birth Control Less Effective?
  • Three Important Questions About Men’s Sexual Health, Answered
  • Here’s The Likelihood Of Getting Jock Itch From A Partner Who Has It

Calendar Based Methods of Contraception

  • What are calendar based methods?
  • How calendar based methods work
  • Who can and cannot use calendar based methods?
    • Standard days method
    • Calendar rhythm method
  • Correct use of calendar based methods
    • Methods of monitoring fertile and infertile periods
      • Standard days method
      • Calendar rhythm method
  • Effectiveness of calendar based fertility awareness methods
  • Benefits of calendar based methods
  • Limitations of calendar based methods

What are calendar based methods?

Calendar based contraceptive methods prevent pregnancy by monitoring the fertile periods during the menstrual cycle. To use this method a woman monitors the length of her menstrual cycle for a period of six months to establish how many days her cycle usually lasts for. She then tracks the progress through each future cycle from the first day of menstrual bleeding (e.g. by numbering the days in a calendar). Doing this enables a woman to determine whether or not she is fertile on a given day of her menstrual cycle and avoid sexual intercourse on those days.

How calendar based methods work

Calendar based methods work allow women to avoid sexual intercourse or use alternative contraceptive methods during the fertile stages of their menstrual cycle.

Research has demonstrated that women are fertile for only around six days of their menstrual cycle, and that the period of fertility coincides with ovulation (the release of an egg from the ovaries). When an egg is released from the ovaries, it enters the fallopian tubes, where fertilisation can occur. If the egg is not fertilised, it travels through the tubes and is expelled through the vaginal opening. This process takes around 24 hours, and it is only within this 24 hours period that fertilisation of the egg can occur.

However, sperm can survive in the fallopian tubes for up to five days following ovulation. This means that if a woman has unprotected sex in the 5 days prior to ovulation, there is a chance that viable sperm, that is sperm which are still alive and have the capacity to fertilise an egg, may remain in her fallopian tubes until ovulation occurs. Therefore, the woman is considered fertile for six days, rather than 24 hours.

In the vast majority of menstrual cycles, ovulation occurs in middle of the cycle. For women who have standard length menstrual cycles (cycles between 26-32 days in length) 94% of women will experience ovulation within 4 days of their cycle midpoint. Thus by calculating the mid point of the cycle, women can also work out when they are potentially fertile, and when they are definitely infertile. Sex can then be avoided or an alternative method of contraception used on the fertile days of the cycle.

Who can and can not use calendar based methods?

Standard days method

The standard days method can be used by any woman who wishes to prevent pregnancy and experiences regular menstrual cycles, between 26-32 days in length.

The standard days method should be used with caution in patients with irregular menstrual cycles (e.g. women approaching menopause).

Calendar rhythm method

The calendar rhythm method is a method in which a woman calculates the fertile and infertile days of her menstrual cycle based on the length of her own cycle (as opposed to using a standard length cycle as is the case with the standard days method). This method can therefore be used by women who have irregular length menstrual cycles (menstrual cycles which are always or occasionally <26 days or >32 days). Women must keep track of the length of their menstrual cycle for at least six months before commencing this method.

Correct use of calendar based methods

Women wishing to use calendar based methods should ensure they are fully informed about correct use, as unless the methods are used correctly, their effectiveness is limited. The correct methods for monitoring fertility according to the standard days and calendar rhythm methods are outlined below, and tools are provided to make calculating the fertile period easier. However women should consult a health professional before commencing use of these methods.

It is also extremely important that women using calendar methods do not have unprotected sex during the fertile period. Women who do not wish to abstain from sex during this period should use another method of contraception, for example a diaphragm, which is often used in conjunction with a spermicide to increase contraceptive effectiveness).

Methods of monitoring fertile and infertile periods

Standard days method

The standard days method involves counting off days as the menstrual cycle progresses. In order to use this method effectively, women should:

  • Consider the first day of menstrual bleeding as day one of the menstrual cycle;
  • Keep track of the days of the menstrual cycle using a calendar or Cyclebeads (a string of beads with different colour codes for fertile and infertile days of the menstrual cycle);
  • Avoid unprotected sexual intercourse between days 8-19 of the menstrual cycle, as this is the period of fertility. Women using the standard days method who wish to have sex in this period should use another method of contraception;
  • The method provides contraceptive protection which is 95% effective between days 1-7 of the menstrual cycle, and from day 20 to the commencement of next period of menstrual bleeding.

Calendar rhythm method

The calendar rhythm method is based on the length of an individual woman’s menstrual cycle. The woman must calculate her fertile and infertile periods based on her own menstrual cycle length. To do this effectively women should:

  • Monitor the length of each menstrual cycle for a period of six months before commencing the method;
  • Continue monitoring the length of each menstrual cycle and always use the most recent six menstrual cycles to calculate the fertile days, as explained below;
  • To calculate the first day in the cycle in which she is fertile, the woman should subtract 18 from the number of days of her shortest menstrual cycle in the six month period. This result is the first day in her menstrual cycle where she will be fertile. For example, if a woman’s shortest cycle was 24 days in length, she would first become fertile 6 days after the first day of menstrual bleeding;
  • To calculate the time in the cycle at which she ceases to be fertile, the woman should subtract 11 from the number of days of her longest menstrual cycle. The result indicates the day in her menstrual cycle from which she is no longer fertile. For example, if the longest cycle was 35 days, the woman would be infertile from day 26 of the cycle).

Effectiveness of calendar based fertility awareness methods

The standard days method is 95% effective. In practice the standard days method is only around 88% effective, as couples using the method do not always abstain from sex during fertile periods. However, as some 85% of sexually active women who do not use any form of contraception will become pregnant within one year, the method still provides considerably higher protection than no contraceptive use.

The calendar rhythm method is 91% effective when used according to the guidelines outlined above.

Benefits of calendar based methods

The benefits of calendar based methods include:

  • They are natural and do not cause side effects;
  • They do not require any special devices or procedures and do not cost anything;
  • Women become more knowledgeable about their menstrual cycle when they use the method.

Limitations of calendar based methods

The limitations of calendar based methods include:

  • Women must monitor the length of their menstrual cycle in order to use them effectively;
  • The standard days method is only suitable for women who have regular menstrual cycles;
  • Constant menstrual cycle length monitoring required for the calendar rhythm method may be difficult for some women;
  • Additional contraceptive methods or abstinence are required for a significant portion of the menstrual cycle;
  • While the methods are theoretically highly effective (91-95%) in practice the standard days method is 88% effective and the calendar rhythm method is 86% effective;
  • They do not protect against sexually transmitted infections (STIs). Women who have sexual partners of unknown STI status should be advised to used male or female condoms to protect against STIs.

More information

For more information on different types of contraception, male and female anatomy and related health issues, see Contraception.
  1. World Health Organisation. Family Planning: A global handbook for providers. 2007. Available from: www.who.int/entity/reproductivehealth/publications/family_planning/en/
  2. Germano, E. Jenning, V. New approaches to fertility awareness based methods: incorporating the standard days and two days methods into practice. J Midwifery Women’s Health. 2006;51:471-7.

Rhythm Method

The rhythm method is a type of birth control. Sometimes referred to under the category of “natural family planning,” or NFP, this approach to birth control involves a woman monitoring when she is fertile and avoiding sexual activity, or using other types of birth control such as condoms, at that time of her cycle. The rhythm method is also called the fertility awareness method.

The rhythm method is not as effective at preventing pregnancy as other methods, such as taking birth control pills ‒ it is only effective about 76 percent of the time ‒ but it appeals to some women who do not like the side effects that are possible with other options. It is also appealing to women who have religious objections to using medical forms of birth control.

Share Facebook Twitter LinkedIn Email Get useful, helpful and relevant health + wellness information enews

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Fertility Awareness

What Is Fertility Awareness?

Fertility awareness is a way to try to prevent pregnancy by not having sex around the time of

(the release of an egg during a woman’s monthly cycle). Couples who want to have a baby can also use this method to plan sex during the time the woman is most likely to conceive. Fertility awareness is sometimes called natural family planning, periodic abstinence, or the rhythm method.

How Does Fertility Awareness Work?

If a couple doesn’t have sex around the time of ovulation, the girl is less likely to get pregnant. The trick is knowing when ovulation happens. Couples use a calendar, a thermometer to measure body temperature, the thickness of cervical mucus, or a kit that tests for ovulation. The ovulation kits are more useful for couples who are trying to get pregnant. The fertile period around ovulation lasts 6 to 8 days. During this time, a couple using only fertility awareness for birth control should not have sex.

How Well Does Fertility Awareness Work?

Fertility awareness is not a reliable way to prevent pregnancy for most people. Over the course of a year, as many as 24 out of 100 typical couples who use fertility awareness alone will have an accidental pregnancy.

It is often very hard to tell when a girl is ovulating. She can conceive for up to 5 or 6 days before she ovulates and 1 or 2 days after. Because teens often have irregular periods, it makes predicting ovulation much harder. Even girls who usually have regular cycles can have irregular timing of ovulation from things like stress or illness. Fertility awareness requires a commitment to monitoring body changes, keeping daily records, and not having sex during the fertile period.

Does Fertility Awareness Help Prevent STDs?

No. Fertility awareness does not protect against STDs. Couples having sex must always use condoms to protect against STDs, even when using another method of birth control.

When Should I Call the Doctor?

Someone who uses fertility awareness should call the doctor if she:

  • might be pregnant
  • has a change in the smell or color of vaginal discharge
  • has unexplained fever or chills
  • has belly or pelvic pain
  • has pain during sex

Reviewed by: Larissa Hirsch, MD Date reviewed: November 2018

  • Larger text sizeLarge text sizeRegular text size

Fertility awareness is a way to try to prevent pregnancy by not having sex around the time of

(the release of an egg during a woman’s monthly cycle). Couples who want to have a baby can also use this method to plan sex during the time the woman is most likely to conceive. Fertility awareness is sometimes called natural family planning, periodic abstinence, or the rhythm method.

If a couple doesn’t have sex around the time of ovulation, the girl is less likely to get pregnant. The trick is knowing when ovulation happens. Couples use a calendar, a thermometer to measure body temperature, the thickness of cervical mucus, or a kit that tests for ovulation. The ovulation kits are more useful for couples who are trying to get pregnant. The fertile period around ovulation lasts 6 to 8 days. During this time, a couple using only fertility awareness for birth control should not have sex.

Fertility awareness is not a reliable way to prevent pregnancy for most people. Over the course of a year, as many as 24 out of 100 typical couples who use fertility awareness alone will have an accidental pregnancy.

It is often very hard to tell when a girl is ovulating. She can conceive for up to 5 or 6 days before she ovulates and 1 or 2 days after. Because teens often have irregular periods, it makes predicting ovulation much harder. Even girls who usually have regular cycles can have irregular timing of ovulation from things like stress or illness. Fertility awareness requires a commitment to monitoring body changes, keeping daily records, and not having sex during the fertile period.

No. Fertility awareness does not protect against STDs. Couples having sex must always use condoms to protect against STDs, even when using another method of birth control.

Someone who uses fertility awareness should call the doctor if she:

  • might be pregnant
  • has a change in the smell or color of vaginal discharge
  • has unexplained fever or chills
  • has belly or pelvic pain
  • has pain during sex

Reviewed by: Larissa Hirsch, MD Date reviewed: November 2018

“At first were worried,” she said, “but then we got used to it and have grown to trust it. I honestly can’t imagine ever going back on the Pill.”

Other women told me the apps simplify what they would have been doing anyway. Rachel, who lives in Scottsdale, Arizona, said she’s been using fertility-awareness methods almost exclusively for 10 years. Before apps like the two she relies upon, Clue and OvuView, came along, she kept a three-ring binder full of temperature readings by her bed.

“My husband has been known to pop the thermometer in my mouth when I wake up and remind me to do cervical checks in the evening,” she said. “It’s brought us closer than ever because he’s so in tune with my body and my natural cycles.”

* * *

The app version of CycleBeads (Cycle Technologies)

Leslie Heyer, president of Cycle Technologies, which makes CycleBeads, told me that its success rate is about 95 percent for “perfect use” and 88 percent for “typical use,” which would mean it beats condoms and falls just short of the Pill. And though women using CycleBeads have only 18 infertile days each month (14 if you deduct menstruation days), Heyer says women using the method have intercourse just as often as those on the Pill.

None of the women I contacted said they had any slip-ups or unintended pregnancies, and some said fertility awareness was just as easy to handle as the Pill or condoms. Rachel even described it as “like breathing.”

However, several of them emphasized that there’s a difference between what they do and the “rhythm method,” a different kind of days-counting technique developed in the 1930s, which doesn’t use temperature readings and which has a historical association with the Roman Catholic church.

Also important is the distinction between apps like Daysy’s and CycleBeads, which are specifically designed for contraception, and those that only track ovulation for couples who are trying to get pregnant. (Clue doesn’t officially bill itself as birth control, for example.) Experts don’t recommend simply repurposing a basic fertility app for contraceptive purposes.

The American College of Obstetricians and Gynecologists said in a statement that, “Natural family planning is not as effective as most other methods of birth control. One in four women who use this method become pregnant.” The organization also said that women who have abnormal bleeding, vaginitis, cervicitis, frequent fevers, or who are on certain medications should not use these methods.

Nathaniel DeNicola, an OB-GYN with the University of Pennsylvania, said natural methods are “definitely not the most effective,” but can nevertheless be a good option for women who are fed up with hormonal methods, leery of copper IUDs, or have health risks that preclude taking the Pill. Because being off by even a few days can result in pregnancy, he says it’s essential women track their days and symptoms vigilantly—and if apps can help with that, so be it.

About the author

Leave a Reply

Your email address will not be published. Required fields are marked *