The Rhythm Method: How Well Does It Work and Who Is It For?

The rhythm method of birth control goes by many names—calendar method, fertility awareness or natural family planning method—but the idea is the same. It’s all about tracking your cycle to figure out your most fertile days.

Some choose the rhythm method for family planning purposes, and others utilize it as a form of contraception. How do experts define the rhythm method? How effective is it? Why do some people use it?

What is the rhythm method?

Using the method involves daily tracking of the menstrual cycle. At the end of each cycle, you mark your calculations to better determine your fertile days.

"The most fertile days are typically the days leading up to ovulation and the day of ovulation itself," said Martha Lee, D.H.S., an AASECT-certified clinical sexologist with a doctorate in human sexuality with Eros Coaching in Singapore. "To determine when these days are, a woman can subtract 18 from the total number of days in her cycle. For example, if her average cycle length is 28 days, then she should avoid intercourse from day 10—28 minus 18—until day 14, the day of ovulation."

People may select another form of contraception, such as condoms or spermicide, to prevent pregnancy or avoid sexual intercourse when the woman is most fertile.

What are other fertility awareness methods?

Those who use the rhythm method may use it with other natural fertility awareness methods, such as the basal body temperature method and the cervical mucus method. It is more effective to combine the rhythm method with basal body temperature and the cervical mucus method.

When these methods are combined, it’s referred to as the symptothermal method.

The basal body temperature method involves tracking your temperature each day throughout the menstrual cycle. Body temperature is lower during the first part of the cycle and increases slightly when ovulating. The cervical mucus method involves tracking vaginal discharge, which increases and changes before and during ovulation.

The standard days method (SDM) involves determining the 12-day fertile window when a woman should opt for a different contraceptive method or skip sex entirely. The Centers for Disease Control and Prevention (CDC) shared that roughly 5 out of 100 women will become pregnant the first year, even when perfectly following SDM.

Is the rhythm method effective at preventing pregnancy?

The rhythm method isn’t as effective as other forms of contraception. It is effective up to 75 percent of the time. Its effectiveness will depend on whether you follow the method correctly and is dependent on having a consistent menstrual period.

According to Mayo Clinic, 24 out of 100 people using this method will become pregnant within the first year. In comparison, hormonal birth control that contains estrogen or progestin—examples are the intrauterine device (IUD), birth control skin patch or vaginal ring—is effective up to 99 percent of the time with perfect use.

Anyone opting for the rhythm method must know it’s not as effective as other contraceptive methods.

"The rhythm method is not a foolproof form of contraception, as it does not account for irregularities in a woman’s menstrual cycle or other factors that can affect fertility," Lee said. "Additionally, it requires a high level of commitment and discipline to ensure that it is used correctly."

Who could benefit from the rhythm method?

"It can be a good option for people who don't like hormones or barrier methods. For some people, it may be their only option based on their religion or culture," said Sue Milstein, Ph.D., a New York-based certified sexologist and a co-author of the 6th edition of "Human Sexuality: Making Informed Decisions."

If getting to a doctor or the cost of birth control is prohibitive, this might be a choice for some.

"[It's] no cost unless you buy an app to help you track, no hormones, no side effects and no need to see a healthcare provider," said Milstein, who is also the founder and lead consultant at Milstein Health Consulting.

Couples trying to conceive can use the method to identify the best times for conception and increase their chances of conceiving, according to Lee.

"It can help couples better understand their bodies and the fertility process and…can be used to identify potential fertility issues," she added.

Fertility awareness methods also have other benefits unrelated to contraception or conception, such as providing insight into a woman’s menstrual cycle, which can be beneficial for overall health, Lee said.

Who may not want to use the rhythm method?

"I have concerns about its effectiveness. Even under perfect conditions, it’s not as effective as other methods," Milstein said. "My other concern is less about contraception and more about infection. The rhythm method doesn’t provide any protection from STIs."

Due to its lack of sexually transmitted infection (STI) protection, it’s not a recommended method for everyone. Condoms and barriers are the only contraception that also protects against STIs.

Lee added that other cons of the rhythm method include:

• It can be difficult to interpret the data accurately.
• If the method fails, can cause anxiety and stress.
• It may be trickier than other methods to follow.

The rhythm method operates under the assumption that someone will know their fertility-likeliness based on a regular menstrual cycle, Milstein said. However, 14 percent to 25 percent of menstruating people have irregular cycles.

Other factors can also disrupt the method’s accuracy. If someone is using the cervical mucus method to better track their cycle, an infection such as bacterial vaginosis (BV) or a yeast infection can cause vaginal discharge and skew the results of tracking ovulation.

What should you know if you choose the rhythm method?

With the rhythm method, as the name suggests, a consistent cadence is critical.

"The rhythm method is better for people who have been menstruating regularly for a while. This means it’s not a great option for teens, people who have recently given birth or people who are coming off of a hormonal method of contraception," Milstein said.

The rhythm method also includes closely monitoring and recording the menstrual cycle each day, which could be an inconvenience. While some women might opt for the use of cycle-tracking apps for better and easier recording, Milstein said that privacy data could be a concern.

"Apps may be helpful, but given the current legal debate in some areas, I would be concerned about having an app that tracks fertility data that others may be able to access," she said. "If a person isn’t using an app, then they need to make sure they have a set routine to stick to for recording the information on their menstrual cycle."

With the protection of Roe v. Wade no longer in effect, experts expressed concern about how data could be shared to criminalize people. However, some period-tracking apps do not allow third-party data tracking and store information locally. Read the fine print before using a period-tracking application.

The bottom line

Watching for fertility signs, documenting your cycle and abstaining from sex (or choosing a different contractive) during fertile times may prove difficult for some people. If you have concerns about your reproductive health, speak with your doctor.

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