An App You Can Use for Birth Control: Does It Really Work?

by Lara DeSanto Health Writer
Natural Cycles

While there are a wide variety of birth control methods available, it can be slimmer pickings for those who want to avoid methods that use hormones, like the pill or the implant. At least, that’s what Nobel Prize-winning physicist Elina Berglund, M.D., found when she decided to switch from the birth control implant to a nonhormonal method.

“I wanted to give my body a break until my husband and I were ready to have children, so basically I started looking for what kind of birth control method I could use in the meantime,” Dr. Berglund tells HealthCentral in a Skype interview. “But I didn’t find any good product on the market, or anything reliable.”

So, being a scientist, Dr. Berglund took matters into her own hands; she would develop an algorithm based on a fertility tracking technique called the basal body temperature (BBT) method. After realizing that other women could likely benefit from this algorithm, she decided to turn it into an app: enter Natural Cycles, the first app to ever be certified as a form of contraception in Europe.

How do you use the app?

Before you get out of bed each morning, you take your temperature with a highly accurate thermometer called a basal thermometer and enter that information into the app. The app will then tell you whether you are fertile that day and thus need to use protection to prevent pregnancy (a red day) or whether you are not fertile that day (a green day).

The app learns more about your cycle the longer you use it, so you’re likely to have more red days in the beginning to be safe, according to the app’s website. You can either sign up for a monthly plan ($9.99/month) or a yearly plan ($6.69 per month and comes with a basal thermometer).

And, of course, it’s important to note that you should still use condoms on green days if you want to protect against sexually transmitted diseases (STDs).

How does it work?

While the Natural Cycles app and other cycle-tracking apps may be relatively new, the concept of tracking your fertile days during the menstrual cycle is not. Fertility awareness-based methods of birth control (also called natural family planning) involve learning to recognize these fertile days, according to the American College of Obstetricians and Gynecologists (ACOG). The method Natural Cycles is based on, the BBT method, is one way to do this. In most women, ovulation will result in a slight increase in body temperature, so tracking that temperature can help a woman predict when she is at risk of getting pregnant.

Sounds easy, right? Well, according to the Centers for Disease Control and Prevention (CDC), these fertility awareness-based methods of birth control aren’t exactly the most reliable options out there. In fact, 24 women out of 100 will become pregnant in the first year of typical use. (“Typical use” means you use the method in the way the average person does, which isn’t always perfectly.)

So what exactly does the Natural Cycles app add to this age-old practice? Its algorithm, Dr. Berglund says. In addition to BBT, the algorithm also takes other factors into account, like sperm survival, temperature fluctuations, and cycle irregularities.

“With the app, we take away the human error in the sense that the woman doesn’t have to have prior knowledge when she starts using the app and doesn’t have to analyze her data herself,” Dr. Berglund says.

The most recent clinical study involving Natural Cycles, published in August 2017 in Contraception, found that using the app as birth control was much more effective than using traditional fertility awareness-based methods — a 6.9 percent failure rate versus 24 percent. This data would also place the app above the birth control pill, which has a 9 percent failure rate, according to the CDC. Long-acting reversible methods of contraception like the intrauterine device (IUD) and implant remain the most effective reversible options, with failure rates lower than 1 percent.

While the app is the first to ever be certified as a medical device intended to be used as birth control in Europe, it’s important to note that it has not received that certification in other countries — although Dr. Berglund says they are in talks with the Federal Drug Administration to get similar designation in the U.S.

For now, the app’s website notes, “In countries outside of Europe … the app is intended to be used for the purposes of fertility monitoring.”

Too good to be true?

While Candace Howe, M.D., an obstetrician-gynecologist based in Newport Beach, California, thinks there are definite benefits to using cycle-tracking apps, she remains skeptical about one that markets itself as a birth control method. One big reason for this? BBT isn’t a reliable fertility tracking method for all women to begin with, she tells HealthCentral.

“Not everyone has an obvious temperature spike when they ovulate,” she says.

Fertility awareness-based methods like BBT are even less reliable for women with irregular periods who may not ovulate regularly or at all, often as the result of certain chronic conditions.

“There are just so, so many women, I take care of them all day long, who have ovulatory dysfunction,” Dr. Howe says. “I’ve had patients … who are following their temps get totally confused. They bring their charts into the office and they have multiple spikes, they don’t know when they really ovulated, and their periods are different each month.”

One major cause of this kind of irregularity is polycystic ovary syndrome (PCOS), Dr. Howe says. One in 10 women has PCOS, according to the U.S. Department of Health and Human Services. It’s a chronic condition caused by an imbalance of reproductive hormones — hormones that affect the BBT.

Other causes of irregular periods include thyroid conditions like hypothyroidism, going through perimenopause, uncontrolled diabetes, and more, according to the National Institutes of Health.

While Dr. Berglund acknowledges that women with certain conditions that cause irregular periods may have more red days when using the app as birth control, she also poses a potential upside: Should women with these issues want to get pregnant, using the app may actually help them learn more about their cycles, which is helpful when trying to conceive.

Additionally, Natural Cycles (and fertility awareness-based methods in general) works best with complete self-discipline, along with total buy-in from your partner to use another birth control method or avoid sex entirely on the fertile days, Dr. Berglund says.

If those things sound trickier, it may be wise to consider other options, such as long-acting reversible methods like the implant or the hormonal or nonhormonal IUD.

“I love the fact that these [long-acting reversible methods], you can just put them in, there’s no user error, and the woman doesn’t have to think about it,” Dr. Howe says.

Is there an ‘ideal’ user?

While having regular periods is not a requirement for using the Natural Cycles app, regular cycles are more likely to result in more green days. Needless to say, having more green days may make using the app for birth control a better experience.

In Dr. Berglund’s view, the ideal Natural Cycles user is also a woman in a stable relationship. In fact, she says, their data show the app’s average user is 29 years old and in a committed relationship.

Dr. Howe agreed that the app could be a good nonhormonal solution for long-term, monogamous couples.

“But for the young college girl, who should be using condoms anyway — any single, monogamous potentially, or maybe [in] a newer relationship woman — they need to protect themselves from bigger things,” Dr. Howe says. “I wouldn’t want them to get false assuredness from this [app], and I’d want them to be very, very careful with barrier protection.”


  • Relatively easy to use (granted you remember to take your temperature at the start of each day)

  • A nonhormonal option backed by clinical studies

  • More effective than traditional fertility awareness-based methods of family planning

  • Like other fertility tracking apps, helps you learn more about your body and your menstrual cycle

  • Good for women in stable relationships who are less concerned about unplanned pregnancy


  • Not ideal for women with irregular periods or abnormally fluctuating temperatures (for example, as the result of a chronic condition like PCOS or hypothyroidism)

  • Like other birth control methods (except for the condom), doesn’t protect against STDs

  • More room for user error: Unlike a set-it-and-forget-it method like the IUD, the app relies on the fact that you will take your temperature properly each day and heed the app’s warnings when it says to use protection. It relies on condom use or abstinence on red days, versus other birth control methods like the pill and IUDs that work to prevent pregnancy every day of your cycle.

  • Currently only certified as a birth control method in Europe

Lara DeSanto
Meet Our Writer
Lara DeSanto

Lara is a former digital editor for HealthCentral, covering Sexual Health, Digestive Health, Head and Neck Cancer, and Gynecologic Cancers. She continues to contribute to HealthCentral while she works towards her masters in marriage and family therapy and art therapy. In a past life, she worked as the patient education editor at the American College of OB-GYNs and as a news writer/editor at