How risky is digital birth control?
In 2018 the FDA released an announcement allowing the Natural Cycles app to market their product in the United States, bringing the first digital birth control to consumers. The Natural Cycles product is a combination of a mobile app with a thermometer. The app contains an algorithm that calculates the days of the month a woman is likely to be fertile based on daily body temperature readings and user-entered menstrual cycle information. To call a spade a spade, this is a digital version of natural family planning or the fertility awareness method where menstruators avoid sexual activity (or use additional precaution like condoms) on fertile days that could lead to pregnancy.
Natural Cycles Product. Image Credit
You may wonder why I’m writing this article so many years after the launch of Natural Cycles in the US. Frankly, I’ve seen an increase in interest among my friends who’ve asked for my opinion on digital birth control as a method of preventing pregnancy. I’ve shared my off the cuff ‘expert answers’ in texts. In order to help a greater number of women in their decision-making process it felt like it was time to share my knowledge in a publicly available location. I’m digging into how well digital birth control works compared to other options, the risks and benefits, the products to chose from, and what to consider before you opt for this method of contraception.
How well does Natural Cycles work?
In 2020 Natural Cycles published a scientific study, Contraceptive Effectiveness of an FDA-Cleared Birth Control App: Results from the Natural Cycles U.S. Cohort.
I read the study so you don’t have to, but I do think you should review the results section:
Results: The study included 5,879 women who contributed an average of 10.5 months of data for a total of 5,125 woman-years of exposure. The average user was 30 years old with a body mass index of 24 and reported being in a stable relationship. With typical use, the app had a 13-cycle cumulative pregnancy probability of 7.2% and a 1-year typical use PI of 6.2. When the app was used under perfect use, the PI was 2.0.
In lay woman terms, this means that with typical use (this assumes human error and not existing within a perfect research environment) 7 women out of 100 will become pregnant within a year using Natural Cycles. With perfect use (and I am speculating a regular menstrual cycle…more on that later) 2 women out of 100 will become pregnant within a year.
I’m putting on my high school gym teacher hat to remind you that no method of contraception is perfect other than abstinence. However, there are many safe and effective methods of contraception that allow for sexual activity and lower pregnancy risk. Let’s compare common options with the typical use efficacy data of other birth control methods just for discussion. I pulled this data from Bedsider.
IUD: 99.2-99.9% effective
Birth control shot: 96% effective
Birth control pill: 93% effective
Natural Cycles: ~93%
Condom: 87% effective
93% efficacy is respectable, but it isn’t as high as other common birth control options. As I researched this article, I discovered that some OB-GYNs questioned whether 93% is accurate given the limited amount of time that Natural Cycles has been available in the market. I think additional studies are necessary to confirm.
What are the risks and benefits of digital birth control?
There are side effects and trade offs with all contraception options. Part of selecting the right one for you is weighing the pros and cons. Every person is unique, every body is unique, and everyone’s preferences are unique. The risks and benefits for traditional birth control are clearly outlined in pharmaceutical packaging. With digital birth control there are various bodily, lifestyle, social and political considerations as part of the risk/ benefit analysis.
Benefit: No artificial hormones
Hormonal options such as the pill, implants, injections, and IUDs have side effects including weight gain, cycle changes, increased risk for blood clots, stroke, mental health changes, and more. One of the reasons women opt for digital birth control is to avoid putting additional hormones in their bodies. If you want a non-hormonal option, that’s a +1 in benefits category.
Risk: Data integrity is paramount and humans are imperfect
I need to state the obvious — only about 13% of women have a perfect 28 day cycle which many fertility algorithms use as a baseline for predicting fertile days and menstruation. If a digital birth control app uses a proprietary algorithm that crunches your individual data to make personalized predictions (the best case scenario) it needs good quality data to make accurate predictions. As we often say in research, “garbage in, garbage out.” If you want to consider a digital birth control method you need to be committed to daily data entry, including taking your temperature at the same time each day if the product includes a thermometer. You may also want to use a back up method for the first 3-6 months while the algorithm learns your body.
Risk: Illness and stress affect menstrual cycles
Stress, rapid weight loss and gain, extreme exercise, illness, medications, and environmental exposures can alter the duration of woman’s menstrual cycle, and in some cases women may skip an entire month. This is detrimental to the algorithm being able to do its job. Let’s say you are exposed to a virus that causes you to have a fever. Your basal body temperature will rise and essentially screw the entire month of data. If anything abnormal is going on in your life, you should use a backup method of contraception. If this annoys you to have to consider how your daily life will affect the efficacy of your contraception, then digital birth control is not for you.
Risk: Data security and our political climate
The Dobbs decision repealed Roe v. Wade. Roe v. Wade previously guaranteed a woman’s right to privacy when it comes to terminating a pregnancy. Overturning this Supreme Court decision has led to a waterfall of restrictive reproductive health legislation across the United States. In January of 2023, the Guttmacher Institute released a map of the US highlighting 24 states with restrictive abortion policies including near total bans. So what does this mean for using digital birth control?
It’s entirely possible that the data from reproductive tracking apps could be subpoenaed for criminal evidence. Therefore, it’s important to ask yourself, “How much of a crisis is a pregnancy?” We already know that digital birth control is less efficacious than other methods and part of the risk/ benefit analysis is considering what would happen in the event of a failure. If you are averse to becoming pregnant any time in the next few years, I’d take a hard look at if this is a good choice for you. If you are spacing between children or ok with an unplanned pregnancy then you may be more willing to accept the risk.
What are your options?
Five years later, Natural Cycles isn’t the only digital birth control product on the market. In 2021, the Clue app, a global favorite for menstrual tracking, was cleared by the FDA as another option for digital birth control. Clue uses the Dynamic Optimal Timing (DOT) machine learning algorithm to identify potential fertile day. A study of an app using DOT indicated similar efficacy rates to Natural Cycles. An important distinction is that Clue Birth Control does not include a temperature component but solely relies on menstrual cycle data for their predictions. In their birth control user manual Clue suggests having 3 ‘regular’ cycles after stopping another birth control method prior to starting use of the app.
Both Clue and Natural Cycles sync with the Oura ring. This means that passive data collected from Oura, such as temperature data, can now be sent into the digital birth control apps. The fine print on the Clue + Oura announcement actually states that the temp data from Oura informing the fertile window should not be used as a means of birth control. Huh.
In Conclusion…
The decision to use digital birth control, like all contraceptive methods, is extremely personal. If you’ve had difficulty tolerating hormonal options in the past, if you are spacing pregnancies, if you are ok with a 93% efficacy rate, if you have a pretty regular cycle (Clue says less than 9 days of variation per month), and if you are dedicated to data collection, then check out Natural Cycles or Clue. I think including temperature tracking and even cervical mucus tracking (fun) would provide the most robust data for decision making and algorithm crunching.
If you want a ‘set it and forget it’ option, then maybe a Long Acting Reversible Contraception (LARC) like an IUD, injection, or implant would make sense. You can talk to your primary care provider or OB-GYN about costs, side effects, and how each might jive with your personal medical history and fertility plans. Need something in the middle? Then check out Bedsider to learn about every option available to humanity.
I am hopeful that as biometrics and devices mature over the next 5-10 years, we will find new biomarkers related to all aspects of women’s health. These advanced insights could increase the reliability of digital birth control and may teach us about our bodies in ways we can’t yet imagine.
If you want to read additional perspectives on the Natural Cycles app from clinicians and fertility specialists, I found this New Yorker article interesting.
