Some women are forgoing synthetic birth control methods in favor of a more hands-on approach—and they're using their smartphones to do it. Here’s what you need to know about the natural family planning method (NFP). 

Couple Laying On Carpet With Cherries
Credit: Stephanie Rausser

Despite the influx of hormone-based birth control options—pills and patches, implants and injections—a small but growing number of millennials are embracing natural family planning (NFP). About 1 percent to 3 percent of women currently rely on NFP as a form of contraception, though a study from the University of Iowa found that 1 in 5 women would consider it as an option if they learned more about it. 

Here’s everything you need to know about the natural family planning method, from proper strategy to typical failure rates.

What is NFP?

This hormone-free birth control option, which is also known as the fertility awareness method or the rhythm method, has been around in some form since the 1950s. NFP involves decidedly low-tech tasks, like taking basal body temperature readings and monitoring changes in cervical mucus to predict ovulation. Many women also track their menstrual cycle to gauge fertility.

Unfortunately, natural family planning is no more effective now than it was decades ago, especially if you have an irregular period. According to the Centers for Disease Control and Prevention (CDC) and the American College of Obstetricians and Gynecologists (ACOG), it's still one of the least effective birth control methods out there. Failure rates range from 12% to 24% with typical use. NFP also offers no protection against STDs, unlike condoms and other barrier methods. 

So why the resurgence in NFP? Millennial devotees swear by the method's lack of devices, medications, and side effects, next-to-nothing cost, and ease of switching gears from avoiding a pregnancy to pursuing one. In fact, NFP can be used on both ends of the baby-making spectrum, since it helps you figure out your most fertile time of the month.

How Does Natural Family Planning Work?

The most bare-bones approach to NFP is tracking your period or basal body temperature (body temperature during rest) on a paper calendar. That way, "a woman gets to know her own menstrual cycle and ovulation rhythms," says Joshua Hurwitz, M.D., a board-certified reproductive endocrinologist and infertility (REI) specialist at Reproductive Medicine Associates in Connecticut.

Here's more information about the common ovulation-tracking methods:

Basal Body Temperature: Women experience a slight, but detectable, rise in body temperature during their fertile period. To use this method, a woman would take her temperature by mouth with a basal body thermometer every morning before getting out of bed, making sure to keep track of the readings. A rise in body temperature that signals ovulation has occurred. To use this form of detection, a couple must abstain from sexual intercourse from the end of the woman's period until three days after the rise in temperature is recorded. As a downside, temperature readings may be affected by fever, lack of sleep, or stress.

Cervical Mucus Tracking:  This method involves detecting changes in how much mucus is produced by the cervix (the mouth of the uterus) and how it feels. For most women, the vagina is dry just after menstruation. Then somewhat sticky mucus appears. Just before ovulation, the mucus becomes increasingly wet, slippery, and stretchy, like raw egg whites. The day when the mucus seems the wettest, called the "peak" day, indicates ovulation. Just after the "peak" day, the mucus may become thick again—or even disappear—and the feeling of dryness returns. Women using this method should be aware that the texture of the mucus can be affected by a vaginal infection, sexual excitement, or the use of lubricants. Checking mucus is best done in conjunction with checking temperature with a basal body thermometer.

When tracking cervical mucus, couples can have intercourse on the 10 or 11 days at the end of the menstrual cycle and the dry days, if any, that occur just after menstruation. The "fertile" period (during which the couple should abstain), starts with the first signs of mucus and continues until four days after the "peak" day.

Symptothermal Method: This method combines the temperature and ovulation methods. It involves taking your temperature every day, checking your mucus, and looking for other signs of ovulation, including breast tenderness, abdominal cramps, vaginal spotting, and a change in the position and firmness of the cervix. Using this method involves abstaining from sexual intercourse from the day you first notice feelings of vaginal wetness until the third day after the rise in temperature or the fourth day after the "peak" day of mucus production.

Period Tracking: In combination with other methods, many women also keep track of their period to predict ovulation. Pay particular attention to the first day of the menstrual cycle (day one) and your period date. Ovulation generally happens about 14 days before your next period is due, says Sharifa Menon, M.D., F.A.C.O.G, an Ob-Gyn at Westchester Medical Center, the flagship of the Westchester Medical Center Health Network (WMCHealth). For example, if you have a 28-day cycle, ovulation would probably occur on day 14. But if you have a 30-day cycle, expect to ovulation on day 16. You're most likely to conceive by having sex on the day of ovulation and the five days before it, says Dr. Menon.

Natural Family Planning Apps

Technology-loving millennials also rely on more than 200 apps to help them pinpoint their windows of fertility, including Daysy, Clue, Glow, CycleBeads, Kindara, Maybe Baby, NaturalCycles, and Ovia. These high-tech helpers help make the job of recording fluids and temperature changes much easier, and they take some of the guesswork out of getting pregnant (or avoiding conception).

In some ways, Dr. Hurwitz isn't surprised at the growing list of tech-driven NFP options. "What don't we do on a smartphone?" he asks. The apps are especially useful for noticing patterns and making accurate calculations, even in women with irregular cycles. "These apps are really smart and self-learning," he continues. "The more data you put into them, the more they can help you."

At the same time, Dr. Hurwitz sees the potential for added stress. Taking daily measurements and inputting seemingly endless numbers can easily become an obsession. Still, he thinks that the benefits outweigh the risks and that the ability to store data is hugely important, especially if a user sees a fertility specialist. "She already has information she can use," he says. "She doesn't have to start from scratch."

It’s vital to note, however, that NFP apps aren't a quick fix. Cycles must be tracked for at least six months before a user can feel confident in her readings. Women need to rely on themselves to properly input the data, as well as the app to accurately calculate it. 

How Effective is NFP?

Of course, even with the high-tech help, natural family planning isn't 100 percent perfect. In fact, the success rates are "all over the map," says Dana Stone, M.D., an ob-gyn in Oklahoma City and a spokesperson for the ACOG. 

Dr. Stone cites that 1 in 5 women out of 100 will become pregnant during the first year of “perfect use”—meaning that the method is used correctly and consistently throughout the menstrual cycle. What’s more, between 12 to 24 women will become pregnant in the first year with “typical use”—the way the average person uses the method, with some incorrectness or inconsistency. 

NFP is less effective than other popular methods of fertility management, like condoms (typical use failure rate of 18 percent), diaphragms (12 percent), oral contraceptives (9 percent) and IUDs (0.2 percent). 

"You have to really be in tune with your body's changes for NFP," Dr. Stone says. She adds that you must also avoid intercourse or use a barrier method during peak fertility. (Your fertile window lasts for several days each month). Also, realize that basal temperature readings are functional only after three consecutive hours of sleep and only if you're not sick. Otherwise, the device may provide a false high.

Should I Use NFP?

In women for whom pregnancy would be dangerous—such as a history of previous pregnancy complications, bleeding complications, high blood pressure, out-of-control diabetes, or a heart condition—a more reliable method of birth control should be used, advises Dr. Stone. But if an unplanned pregnancy isn’t a huge deal, you might want to give natural family planning a try.

But make you sure you understand the ins and outs before relying on NFP as your only birth control method. "Don't think you have it down after a month," says 34-year-old Kathleen Flippen, who first used a fertility tracking app in 2010, "This is especially true if you're coming off of hormonal birth control."