Earlier this month, the FDA announced it cleared another cycle charting app for contraceptive use—this time it is the app called Clue Birth Control. In 2018, the FDA cleared the app Natural Cycles to be marketed as a medical device for contraceptive use, and many wonder if this is the dawn of FemTech possibilities, offering hope to women who are sick of birth control side effects yet still want reliable contraception.
There are some important clarifications that must be mentioned upfront: the Clue Birth Control app offers a different feature from the currently available Clue app. On the Clue website, it states that if you’re interested in receiving the Clue Birth Control capabilities, you can sign up to get notified once it is available. It is also important to note that this Clue Birth Control app is, unlike other fertility awareness methods, not intended for use for people who have irregular cycles and may not be effective birth control for them. It is also not effective for women who have recently used hormonal birth control.
The FDA device summary for Clue Birth Control states that its indications for use are “for contraception for women ages 18 – 45 years old, to monitor their fertility and prevent pregnancy. Clue Birth Control is suitable for women with predictable 20 – 40 day cycles, who have not recently used hormonal birth control.” Within that limited demographic, Clue was found to have a 3% failure rate with perfect use, and 8% failure rate with typical use.
Part of why Clue cannot work with irregular cycles is because it is a calendar-based method of charting. The only data it requires of users is the start date of one’s period, and from there it estimates the next period date, as well as the fertile time around ovulation. Until this recent FDA clearance, however, Clue was considered primarily to be a period-tracking app and not an effective contraceptive option. As recently as 2020, when we evaluated major fertility charting apps in an article for Natural Womanhood, Clue stated on their website that the app functioned primarily as a health tracking device and stressed that it was not to be used on its own as a method of pregnancy prevention.
The important difference between calendar-based methods and symptom-based methods of fertility awareness
Calendar-based methods of fertility awareness can work for some women, who have very predictable cycles, to avoid or achieve pregnancy based on the timing of sexual activity near their estimated ovulation dates. But users considering calendar-based methods should be informed of how they are very different from, and often less effective for pregnancy prevention, than fertility awareness methods that track fertile signs.
To quote our brief explainer on what makes calendar methods different from other modern fertility awareness methods:
“Calendar-based methods” is the blanket term for the rhythm method (first formalized in the 1930s) and the standard days method (introduced in 2002). The rhythm method is a predictive method, which uses a woman’s historically longest and shortest cycle lengths, in order to predict when she will ovulate during her next cycle…. While the standard days method, Cycle Beads, and apps developed from these predictive models are natural forms of birth control, they don’t provide users with knowledge of their fertility signs and the valuable health information that comes with it. These predictive methods also have lower effectiveness rates than methods that train women to observe and chart their body’s unique signs of fertility in real-time.
While some mistakenly think that regular menstrual cycles are a prerequisite for all charting methods of pregnancy prevention, it is important to note that modern fertility awareness methods—specifically, those that measure biological symptoms of fertility in a woman’s cycle, like the Creighton, Billings, FEMM, Sympto-Thermal, and Marquette methods—can be used as effective pregnancy prevention for women no matter her cycle length or regularity, if she learned from a certified instructor. Further, one’s charting data showing cycle irregularities can assist a woman in receiving diagnosis and treatment for menstrual problems and reproductive disorders.
How did Clue Birth Control get FDA cleared?
According to a statement at the Clue website, “The United States Food and Drug Administration (FDA) has classified Clue Birth Control as a software application that can be used as a contraception [sic]to prevent pregnancy. We have been cleared to offer Clue Birth Control to users in the United States of America after submitting extensive information about the feature’s efficacy, the research behind it, and the processes our team has in place to make sure the app is built to the safety standards of a medical device.”
The Clue website further states, “The research to support the effectiveness of Clue Birth Control was conducted by the Institute for Reproductive Health (IRH) at Georgetown University. These researchers conducted a full-scale clinical trial to test the effectiveness of the Clue Birth Control algorithm used to predict high and low risk days of pregnancy.”
The statement from Clue is published alongside the 2018 study showing the effectiveness of its algorithm, which is also known as Dot. The study explains:
Dynamic Optimal Timing (Dot) is a digital, algorithm-based FABM that provides direct-to-user fertility information to women who wish to prevent or plan a pregnancy. Dot’s algorithm, which was developed based on a large dataset of 8118 cycles in 706 women from five countries (New Zealand, India, Ireland, Philippines and El Salvador), taken from World Health Organization and other studies of conception probability, adapts to an individual woman’s cycle length and variability as she continues to enter her menstrual period start dates. When a Dot user enters her menstrual period start date into the app, the app identifies days when she is at ‘high’ or ‘low’ risk of pregnancy in that cycle. For the first cycle, Dot identifies 16 days as high risk. As additional menstrual period start dates are entered, the algorithm narrows the number of days identified as high risk to 11–13 days depending on the user’s cycle lengths and variability.
The study concludes, “As a non-hormonal method that can be offered to women independently of traditional health systems, Dot has the potential to be a valid, feasible addition to the contraceptive method mix. Direct-to-user messaging through the Dot app gives women immediate access to critical fertility information and encourages correct, consistent use.”
Comparing Clue Birth Control to the other FDA-cleared app, Natural Cycles
The FDA device summary for Clue Birth Control states that they “have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to legally marketed predicate devices.” The predicate device cited by Clue in the materials submitted to the FDA is the Natural Cycles app.
But there is a major difference between the two apps: Clue Birth Control is a calendar-based method, and Natural Cycles is a symptom-based method of fertility awareness.
Natural Cycles requires users to provide information on their basal body temperature (BBT), which can be informative about when a woman is fertile and when she is infertile. Natural Cycles is unique in that it is one of the only methods that estimates one’s fertile period using only temperature measurements. (As a side note, the Sympto-Thermal method uses both cervical mucus measurements and basal body temperature measurements, and, with that greater amount of fertility information, it has greater precision evidenced by its higher effectiveness rates. The Sympto-Thermal method boasts a perfect use failure rate of 0.4% and a typical use failure rate of 1.8%. In comparison, the Natural Cycles app reports a perfect use rate of 2% and a typical use failure rate of 7%.)
On its FDA device summary, Clue Birth Control notes that the only data it requires from users is “period start date.” In contrast, Natural Cycles requires: “Menstrual cycle information (period start date and number of days)”; “Daily basal body temperature measurements”; and “Optional: ovulation or pregnancy test results.”
While Clue admits in its FDA documentation that the user input data from its app includes far less information than the Natural Cycles app, it concludes nonetheless that its “intended use and technological characteristics combined with performance data demonstrates that Clue Birth Control, for its intended use population, is as safe and effective as the predicate device [Natural Cycles].”
Elina Berglund, co-founder and CEO of Natural Cycles responded to the news of Clue’s FDA clearance in a statement, saying:
“We’re aware of a period tracker recently receiving FDA clearance, meaning that it too can market itself as a contraceptive. This clearance was granted as an abbreviated 510k that claims equivalence to Natural Cycles. As a leader within this field, we feel it’s our responsibility to uphold the highest standards and after our initial findings based on the FDA filing indicate a significant difference between Natural Cycles and this other product—including that this product is solely based on menstrual data and no other biomarker such as temperature—our medical and research teams will be doing an independent analysis.”
Further, the Natural Cycles website provides an overview of how Natural Cycles Birth Control is different from “the period tracker” (Clue), including that Natural Cycles “confirms ovulation” while the period tracker does not and that Natural Cycles’ research employed a larger data set in its clinical trials and has continued to accrue real-life user data supporting its initial findings.
Is Clue just a glorified version of the Rhythm Method?
After hearing the news of Clue’s FDA clearance as birth control, and seeing that it is primarily a period-tracking app that tells users to use barrier methods of contraception on estimated fertile days, I thought, this seems to be just like an antiquated calendar-based method of charting with the added effectiveness rate of barrier methods. Rachel Wilkerson, a data scientist who has written on fertility charting apps for Natural Womanhood in the past, cleared this up for me: “Algorithms appeal because they give a black and white answer. One of their drawbacks though is that without individual knowledge of how to read biomarkers, the algorithm becomes a bit of a black box. Cutting-edge algorithms can be very accurate, but they may not be as accurate for different subgroups in a population.”
In sum, Clue Birth Control collects less user health data and works for fewer people as a result, because its calendar estimates won’t work for anyone with irregular cycles. While women with irregular cycles can’t trust Clue Birth Control to be effective natural family planning for them, the good news is there are effective symptom-based methods of fertility awareness women can trust to provide high efficacy rates, no matter her cycle length, if she is taught by a certified instructor.
Note: The use of condoms with fertility awareness methods can reduce the effectiveness of pregnancy prevention, and some charting apps that suggest condom use on fertile days do not disclose participants’ rate of condom use in their research. The modern fertility awareness methods that enjoy the highest effectiveness rates of pregnancy prevention require abstinence from sexual activity during the fertile days. This also works for couples who value a philosophy of natural family planning.
Additional Reading:
Is your period and ovulation tracker app legitimate?
Can You Trust Fertility Tracking Apps with Your Data?
‘The Guardian’ Publishes A False Report on Fertility Awareness App
Before Switching to a Fertility App, Consider This
New Fertility Apps Reveal Women Desire to Understand Their Cycles
