Natural Cycles’ effectiveness has generated significant interest as the first FDA-cleared birth control app in the United States. Many women now look to this tech as a non-hormonal birth control option instead of hormone-based contraceptives. But before choosing it as your method of natural family planning, you need to understand its contraceptive efficacy.
Scientific studies provide important information about the effectiveness of Natural Cycles that anyone considering this fertility awareness-based method should be aware of. The app shows a typical use Pearl Index of 6.2, meaning about 6 women out of 100 who use it will experience unintended pregnancies. Use of the app significantly reduces the pregnancy rate; specifically, it drops to only 2 pregnancies per 100 women. The effectiveness of Natural Cycles as a birth control method varies depending on the contraceptive options people used previously. Women who switch from condoms have a lower chance of getting pregnant (3.5) compared to those who switch from the pill (8.1).
This article examines how well Natural Cycles works as a method of pregnancy prevention, based on numerous studies of different groups. We will explain the science behind the ovulation tracking system of Natural Cycles, examine real-world success rates, and discuss the factors that influence how effectively this hormone-free birth control works on a daily basis. If you’re considering using this app for reproductive health management or just want to know more about non-hormonal contraception options, our fact-based review will help you decide if Natural Cycles is worth it for you.
How Natural Cycles Works as a Birth Control App
Image Source: Ars Technica
The main idea behind Natural Cycles is to keep track of small temperature changes in your body during your menstrual cycle. This digital method of natural family planning differs from older fertility awareness-based methods, which required manual charting. Instead, it uses a computer algorithm to analyze your personal information and determine your fertile window.
Body temperature at rest and ovulation detection
Natural Cycles relies on your basal body temperature (BBT)—the lowest temperature your body reaches when you’re resting. This key measurement shows your cycle’s progress due to hormone changes during ovulation.
Your body temperature stays a bit lower before you ovulate. After ovulation occurs, your body releases progesterone. This hormone makes your temperature rise by about 0.3°C to 0.6°C (0.5-1°F). Your temperature remains elevated until just before your period begins.
To optimize the app’s ovulation prediction capabilities, you should:
- Check your temperature immediately upon waking, before sitting up or getting out of bed
- Stick to one method of measuring
- Take your temperature at approximately the same time each day (within a 2-hour window)
- Sleep for at least three hours without interruption to get an accurate reading
Taking measurements at least five times a week leads to the best outcomes. Less frequent measurements won’t affect the contraceptive’s efficacy but might increase the number of days when you need protection.
Red and green day system explained
After you log your temperature, the Natural Cycles algorithm analyzes this data to determine your daily fertility status, displayed as a color:
Green days indicate you’re not fertile. The app displays a green circle with “Not fertile” text these days. The algorithm assigns Green Days when it’s confident—based on your data—that you’re not fertile, either because
- You’ve already ovulated this cycle, or
- You won’t ovulate in the next five days (accounting for sperm longevity)
Red days show when you might be fertile. They appear as a red circle saying “Use Protection.” Red Days covers your fertile window (six days each cycle) plus extra days as a precaution if your cycle varies. On these days, you need to use condoms or abstain from intercourse.
Remember, the app indicates fertility status from one midnight to the next. This result can change if you input new information. That’s why it’s crucial to check the app daily before intercourse, rather than making assumptions.
The app requires time to learn your body’s patterns. Consequently, new users often see more red days initially. As it gathers more data about your menstrual cycle patterns over time, you’ll receive more Green Days.
Optional LH tests for enhanced accuracy
While Natural Cycles primarily relies on temperature tracking, users can also employ luteinizing hormone (LH) tests to improve ovulation detection. These tests analyze urine samples to identify the LH surge that occurs 24-48 hours before ovulation.
The app suggests when to perform these tests by displaying an ovulation test symbol on optimal testing days. Users who record positive ovulation tests might receive approximately 5% more Green Days in each cycle.
A positive LH test indicates imminent ovulation but doesn’t guarantee it will occur. To confirm ovulation, the app’s system still requires the characteristic temperature increase following the LH surge. Negative LH tests do not signify infertility; they simply indicate that the test didn’t detect a surge.
For individuals with conditions like PCOS, doctors don’t recommend LH testing because “false” LH peaks can occur without actual ovulation. Ultimately, temperature data remains the primary factor in the algorithm’s calculations, with LH tests providing supplementary information.
Understanding Natural Cycles Effectiveness Metrics
Image Source: Natural Cycles
To measure contraceptive efficacy, we need standard metrics to help users make informed choices. For Natural Cycles, these measurements demonstrate how this digital fertility awareness method compares to other birth control options.
Typical use vs perfect use
Typically, we categorize contraceptive effectiveness into two distinct groups to get a comprehensive picture of reliability. Typical use reflects real-world usage with all its human imperfections, while perfect use represents ideal conditions when people use a method exactly as intended.
For Natural Cycles, typical use effectiveness ranges from 93–94% across several studies. This ratio means that about 6–7 women out of 100 will experience unintended pregnancies within one year of use. This percentage includes all possible reasons for pregnancy—whether due to unprotected intercourse on red days or despite following the app’s guidance.
Conversely, perfect use effectiveness reaches 98-99%, with research indicating Pearl Indices of 1.0-2.0. Perfect use involves consistently checking temperature and adhering to safety precautions on red days. These figures only account for pregnancies that occur due to method failures, such as condom breakage or the algorithm incorrectly labeling a fertile day as safe.
Pearl Index and 13-cycle failure rate
Contraception experts use two key measures to gauge effectiveness. The Pearl Index (PI) represents the number of unintended pregnancies per 100 women using a method for a year. A lower PI indicates better effectiveness—for instance, a PI of 7 means that 7 out of 100 women would get pregnant in a year.
Studies on natural cycles reveal a typical use of the Pearl Index, from 6.1 to 7.0, depending on the specific research. The largest study, which included 22,785 women from 37 countries, found a typical use-pearl index of 6.9, adjusted to 6.8 when limiting users to 12 months [121].
The 13-cycle failure rate offers an alternative perspective, showing the percentage of women who become pregnant over approximately one year of menstrual cycles. Research indicates Natural Cycles has a 13-cycle typical use failure rate of 8.3%, with variations from 5.5% to 8.6% across different countries.
Also, research showed that pregnancies caused by mistakes in the algorithm (when fertile days were wrongly marked as infertile) were uncommon, occurring in only 0.5 pregnancies for every 100 woman-years, which is just 0.05% of the days that were incorrectly labeled as non-fertile.
Understanding the statistics
To grasp these effectiveness measures, context is essential. Natural Cycles proves more effective than many other methods—surpassing traditional calendar-based fertility awareness methods (24% failure rate) or typical condom use (8% failure rate).
However, the effectiveness of Natural Cycles varies significantly depending on several factors:
- Previous contraceptive history—Women who switched from condoms had better results (PI: 3.5) than those who changed from hormonal pills (PI: 8.1) [101]
- Hormonal history—Women without recent use of hormonal contraceptives showed a lower PI (5.1) compared to those who used hormonal methods (PI: 7.5) [101]
- Age group—Women between 29 and 34 years old had a higher chance of pregnancy (8.8%) compared to those aged 35-45 (5%)
- Protection methods— On fertile days, about 53% of users reported using condoms, 11% abstained from intercourse, and 25% practiced withdrawal
The study demonstrates that Natural Cycles is more effective than traditional fertility awareness-based methods, but it’s not as reliable as long-acting reversible contraceptives like IUDs. Understanding these statistics helps users set realistic expectations about their pregnancy prevention chances based on their individual circumstances and how they use the app.
What Affects How Well Natural Cycles Works in Real Life
Using any fertility tracking method in day-to-day life significantly impacts its effectiveness. With Natural Cycles, three main factors are key to determining real-world results.
How well users follow instructions and log their data
The consistency of temperature readings has a major influence on Natural Cycles’ effectiveness. The algorithm uses temperature data as its primary input to determine fertility, and it recommends taking it immediately upon waking. In practice, people’s measuring habits vary considerably. Research indicates that only 27% of users take readings as frequently as recommended – on 70% of cycling days. Another 19% took measurements on 50–70% of days, while the majority of users—54%—measured on less than half of their cycle days.
The timing of temperature measurements is crucial. The app recommends taking temperature.
- Immediately upon waking, before leaving bed
- Following at least three hours of uninterrupted sleep
- Within the same two-hour window each day
However, these ideal conditions often conflict with real-life situations. People with irregular sleep patterns, night shifts, or young children often struggle to maintain consistent measurement times.
Protection on fertile days
Natural Cycles’ success depends on using effective protection during fertile days. The app advises using condoms or abstaining from intercourse on Red Days, but user behavior varies significantly. Of those who reported their protection methods, 52.5% used condoms, 27.7% practiced withdrawal, and 9% avoided sexual activity altogether.
Natural Cycles explicitly advises against using withdrawal on Red Days, considering it unprotected intercourse when calculating method effectiveness. Nevertheless, over 25% of users opt for this less reliable option.
Consequently, adherence to protocol is low. 7% of all cycles, representing 12% of users, follow the recommended guidelines.
How past birth control affects things
Previous contraceptive methods significantly impact Natural Cycles’ effectiveness for individual users. Those who switched from condoms demonstrated notably better results, with Pearl Index figures substantially lower than those transitioning from hormonal methods.
Furthermore, women who previously used hormonal contraception had a Pearl Index of 7.6, while those coming from non-hormonal methods showed an improved PI of 4.8. This disparity persists even after accounting for other factors, suggesting that the transition itself influences adaptation to the method.
The most common previous methods include
- Hormonal birth control (64.2%)
- Barrier protection (12.9%)
- Withdrawal (8.4%)
This pattern helps explain effectiveness variations, as former condom users tend to adhere better to protection recommendations on Red Days, thus achieving superior real-world effectiveness.
Demographic Insights from Global and Regional Studies
Studies reveal intriguing trends among Natural Cycles users worldwide. Understanding the demographic profile of those who use this digital fertility monitoring method helps contextualize its real-world effectiveness.
Age and relationship status
Research from various countries indicates that Natural Cycles users often fit a specific profile. The typical user is approximately 30 years old, with studies in different regions finding average ages between 27.3 and 30.3 years. A study in Canada found that 91.1% of users were younger than 35.
Family planning status shows clear patterns. The majority of users report being in stable relationships, with research revealing that 83–86% of participants have long-term partners. Moreover, most users are nulliparous, with one study noting 88.7% of participants had never given birth.
It’s worth noting that Natural Cycles’ effectiveness varies significantly with age. Women aged 29-34 had a considerably higher chance of pregnancy (8.8%) compared to users aged 35-45 (5%).
Education level and lifestyle
Natural Cycles attracts a well-educated user base. Studies indicate that 73-84% of users have a university degree or higher [202][223][224]. This educational background may influence users’ comprehension of fertility awareness concepts and adherence to the app’s guidelines.
Physical characteristics among users show some patterns. The average body mass index (BMI) ranges from 23.4 to 24.6 across studies [202][223][224]. An important finding reveals that women with a BMI of 35–50 exhibited 14% more variability in cycle length compared to those with a normal BMI.
Country-specific effectiveness data
Natural Cycles’ effectiveness varies across different countries. A large study examining 22,785 women in 37 countries found notable differences in failure rates with typical use:
- Sweden: 13-cycle failure rate stands at 6.7%, Pearl Index is 6.1
- United Kingdom: 13-cycle failure rate reaches 6.3%, Pearl Index hits 5.8
- Australia: 13-cycle failure rate totals 5.5%; Pearl Index equals 5.1
- Finland: 13-cycle failure rate amounts to 8.6%, Pearl Index comes to 7.5
- Canada: 13-cycle pregnancy probability comes in at 4.8%; Pearl Index sits at 4.3
These regional differences highlight how user behavior, healthcare systems, and cultural attitudes toward fertility awareness methods vary across countries.
Limitations, Criticisms, and Scientific Debates
While Natural Cycles has gained popularity as a non-hormonal contraception option, scientists question its methods and marketing claims. The medical community raises concerns about several aspects of this digital birth control approach.
Self-reporting and data gaps
Research on Natural Cycles’ effectiveness faces a significant limitation: substantial gaps in data collection. One study found that 26.5% of recorded pregnancies occurred in cycles where users didn’t report any information about sexual activity. Furthermore, only 16.6% of participants answered questions about protection methods on red days. These data gaps complicate the calculation of perfect-use rates, potentially skewing the results.
Moreover, pregnancy reporting relies on user initiative. A former user mentioned she didn’t report her pregnancy after using the app. Such behavior suggests that official pregnancy figures may underrepresent the app’s failure rate. Relying on users to report pregnancies introduces uncertainty in assessing the app’s true effectiveness.
Ad bans and controversies
Natural Cycles has encountered regulatory issues regarding its advertisements on multiple occasions. In 2018, the UK Advertising Standards Authority instructed the company to cease running Facebook ads. These ads described the app as “accurate” and a “tested alternative to birth control methods.” The authority deemed these claims misleading and exaggerated.
Since then, the company has modified several of its marketing claims.
- Removing the “99% effective with perfect use” claim following regulatory scrutiny
- Shifting focus to highlight the 93% typical-use success rate
- Incorporating clearer warnings about factors affecting accuracy
Concurrently, Sweden’s Medical Products Agency investigated the app after a hospital in Stockholm reported that 37 of the 668 women seeking abortions were Natural Cycles users who experienced unintended pregnancies.
How it stacks up against other birth control methods
The Society of Obstetricians and Gynecologists of Canada suggests that Natural Cycles’ effectiveness data “might be too high” due to the study population’s lack of representativeness. The majority of participants in the study were college-educated women in heterosexual relationships who purchased the app, a demographic that doesn’t reflect the general population.
Unlike traditional fertility awareness-based methods that require tracking at least six cycles before use, Natural Cycles allows immediate use of the app for birth control. They acknowledge that their algorithm improves over time, starting at about 40% accuracy and reaching 50% after three months.
It’s important to note that 7 out of 12 studies published about Natural Cycles received funding from the company itself or were authored by its employees, raising questions about research impartiality.
Conclusion
As the first FDA-cleared birth control app, Natural Cycles has made a significant impact in the realm of fertility awareness-based methods. This article has thoroughly examined the science behind their effectiveness claims and identified key considerations for anyone contemplating its use as a form of non-hormonal birth control.
Analyzing the data, Natural Cycles demonstrates superior results compared to traditional fertility tracking methods. However, it falls short of the effectiveness of hormonal contraceptives or IUDs. The typical use success rate of 93-94% translates to about 6-7 out of 100 women experiencing unintended pregnancies each year. Perfect use can improve these figures, but real-world studies indicate that only 7% of all cycles adhere to all protocol requirements.
User demographics significantly influence the app’s effectiveness. Women transitioning from condoms show better results than those switching from hormonal birth control. Additionally, factors such as age, educational attainment, and consistent daily temperature monitoring substantially impact its efficacy.
Valid concerns have been raised regarding incomplete data and potential underreporting of pregnancies. The reliance on self-reported information introduces uncertainty in effectiveness assessments. Furthermore, Natural Cycles’ funding of numerous studies has led some to question the impartiality of the research.
Before opting for this app as a method to avoid pregnancy naturally, women should carefully consider their lifestyle, ability to adhere to routines, and comfort with the risk of unintended pregnancy. Those with irregular schedules or difficulties in daily data logging might want to explore alternative contraceptive options. Natural Cycles is most effective when users consistently monitor their temperature and employ additional protection during fertile periods.
Women require clear, science-based information about all available contraceptive options. Natural Cycles offers a novel, hormone-free approach to pregnancy prevention, but its effectiveness hinges on individual factors, consistent usage, and a thorough understanding of its capabilities and limitations. Ultimately, the choice of birth control should align with one’s lifestyle, priorities, and acceptable level of pregnancy risk.
FAQs
Q1. How well does the Natural Cycles app work to prevent pregnancy?
With typical use, Natural Cycles prevents pregnancy 93-94% of the time, which means that 6-7 women out of 100 might experience unintended pregnancies in a year. Perfect use can improve effectiveness to 98%–99%.
Q2. What factors impact the effectiveness of Natural Cycles?
The app’s efficacy depends on user adherence to instructions, consistent temperature monitoring, protection use on fertile days, and previous contraceptive methods. Women transitioning from condoms and those without recent hormonal birth control use often achieve better results.
Q3. Who uses Natural Cycles?
The typical Natural Cycles user is around 30 years old, well-educated (with a college degree), in a long-term relationship, and nulliparous. Most users are under 35 and have a normal BMI.
Q4. How does Natural Cycles compare to other birth control methods?
Natural Cycles demonstrates higher effectiveness than traditional fertility awareness-based methods but doesn’t match the efficacy of hormonal contraceptives or IUDs. It outperforms typical condom use, but users must strictly follow guidelines for optimal results.
Q5. What are some limitations of the Natural Cycles app?
The app heavily relies on self-reported data, potentially creating information gaps and underreported pregnancies. Its effectiveness varies based on user demographics and lifestyle factors. Additionally, while the app allows immediate use, it acknowledges that its calculations improve over time.
