Zara Risoldi Cochrane, PharmD, MS


January 08, 2019


Can an app replace your patients' birth control?

Response from Zara Risoldi Cochrane, PharmD, MS
Associate Professor of Pharmacy Practice, Creighton University School of Pharmacy and Health Professions; Director, Center for Drug Information & Evidence-Based Practice, Omaha, Nebraska


A mobile app designed to prevent pregnancy made headlines earlier this year when it became the first medical application cleared by the US Food and Drug Administration (FDA) for the purposes of birth control. The science behind the app isn't new—fertility awareness-based methods of contraception have been used and studied for decades—but questions remain about the Natural Cycles app, and whether a software program can truly replace your patients' birth control.

The App

The Natural Cycles app uses a fertility awareness method based on basal body temperature (BBT). Women enter their temperature into the app each morning, as well as information regarding their menstrual period. Using a proprietary algorithm, Natural Cycles analyzes BBT trends to accurately predict a woman's daily fertility.[1]

The results are depicted using a simple color-coded graphic. A green circle indicates that the user is not fertile and can have intercourse without the need for additional protection against pregnancy. A red circle indicates a fertile day and alerts the user to use protection (such as a condom) or abstain from intercourse.[2] Natural Cycles learns a woman's cycle as more and more information is entered into the app, making its predictions more accurate with continued use.

In addition to BBT and menstruation, users can choose to track their luteinizing hormone levels (this requires a separate urine test strip). In predicting fertility, the app's algorithm accounts for temperature fluctuations; sperm survival; ovulation day; and variations in menstrual cycle length, including the follicular and luteal phase. What makes Natural Cycle unique from other fertility awareness-based methods is that it digitizes and automates this analysis, eliminating the need for patients to manually chart and interpret their data.[1]

Natural Cycles requires an Internet connection and is compatible with Android and iOS smartphones, as well as other devices with a Web browser.[2] The cost of the app is $9.99 per month or $79.99 for an annual subscription.[3] A free 1-month trial is offered for new users.

Is It Effective Birth Control?

Natural Cycles is promoted as being 93% effective at preventing pregnancy. According to the FDA, the app has a "typical use" failure rate of 6.5% and an "ideal use" failure rate of 1.8%.[4] This puts it roughly on par with injectable contraceptives (typical use failure rate, 6%) and more effective than oral contraceptives (9%).[5]

However, critics have argued that the 93% effective rate is artificially inflated. This statistic was derived from a prospective observational study that evaluated the efficacy of the app in 22,785 women.[6] But the study only looked at patients who were already paying users of the app, potentially introducing selection bias and skewing the results. Women who signed up for a free trial and didn't like the app or who weren't able to keep up with measuring and reporting their BBT every day weren't likely to become paid users—and therefore weren't represented in the study.

According to the Centers for Disease Control and Prevention, fertility-based awareness methods of contraception have a typical use failure rate of 24%.[5] However, this is a broad category that includes family planning through the "rhythm method" and other techniques that do not include biomarkers, such as BBT. On the basis of the available clinical data, Natural Cycles is at least as effective as other widely used and FDA-approved methods of birth control. To date, no studies have compared Natural Cycles with oral contraceptives.

Patient Counseling Points

If your patient is interested in Natural Cycles, consider whether she is a good candidate for using a contraception app.

Can she reliably measure and report her temperature every day? Natural Cycles recommends entering BBT at least 5 days per week. Tell patients to measure BBT first thing in the morning, before getting out of bed, going to the bathroom, or eating or drinking anything. Make sure patients know to use a basal thermometer, which is more sensitive than a regular thermometer. A basal thermometer is included with an annual subscription to Natural Cycles, or one can be purchased for less than $20 at most pharmacies.

Is your patient willing to use protection or abstain from sex on fertile days? Remind patients that Natural Cycles does not protect from sexually transmitted infections, and that no birth control is 100% effective in people who are sexually active.

Tell patients that Natural Cycles gets more accurate the longer they use the app. At first, Natural Cycles will err on the side of caution—that is, giving women more "red" or fertile days. This can be frustrating for new users. After 3 months of regular use, women should expect to have "green" or nonfertile days 60% of the month.[7]

Conditions that affect BBT or ovulation can affect the accuracy of Natural Cycles. Examples include thyroid disorders, polycystic ovary syndrome, breastfeeding, and irregular menstrual cycles, as well as lifestyle factors, such as an irregular sleep schedule, smoking, and excessive alcohol consumption.[2,7] Women with any of these characteristics may not be good candidates for using Natural Cycles.

Patients switching to Natural Cycles from oral contraceptives can start using the app the day after they finish the active pills in their current packet. Patients switching from an intrauterine device, implant, or transdermal contraceptive can start using the app the day after it is removed. Patients switching from a contraceptive injection should wait until the effect of the injection has worn out, which ranges from 8 to 13 weeks.[2]

Make sure you ask patients why they are using Natural Cycles. The app also has a mode to help plan a pregnancy, allowing women to track when they are most fertile and ready to conceive. This mode presents results differently from the contraception mode, so it is important to understand your patients' goals for using the app.

Cleared by the FDA

The FDA cleared Natural Cycles to be marketed to premenopausal women at least 18 years of age. When evaluating mobile apps, the FDA applies the same regulatory approach they use to ensure the safety and effectiveness of other medical devices.[8] This means that the manufacturers of medical apps must abide by rules for product labeling, put procedures in place to ensure their apps are safe and effective, and report errors or injuries that result from using the app.[9]

The FDA categorized Natural Cycles as a Class II medical device, indicating a moderate level of risk associated with its use. This is the same classification assigned to barrier methods of contraception, such as condoms and diaphragms.[8,10]

The Bottom Line

Natural Cycles offers a new option for women interested in nonhormonal contraception, whether because they prefer a more "natural" approach to family planning or because they want to avoid adverse effects associated with birth control. Assess whether patients are good candidates for fertility awareness-based methods and whether they have any conditions that would interfere with BBT. Remind patients to use backup protection on fertile days or for protection against sexually transmitted infections.

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