In recent years, millions of women have turned to apps to track their menstrual cycles and fertility. Yet science has been slow to catch up, leaving us somewhat in the dark on whether the growing reliance on digital technology is a win or fail for women’s health.
Fortunately, a recent independent study of two apps (including Kindara!) showed they provide true insights into the menstrual cycle, ovulation, and fertility signs. The research was published in a credible journal affiliated with Nature, one of the most esteemed scientific journals, (1).
Whether you’re an avid fertility app user or just wondering whether they work, read on as we unpack the meaning of this new science for your fertility and overall health.
Do fertility apps work?
One of the chief aims of the research was determining whether the two fertility apps were effective at detecting and estimating the time of ovulation. It’s critical to know when ovulation is near because the vast majority of pregnancies occur in the 5 days before ovulation, and on ovulation day itself (1, 2).
At the same time, the researchers wondered whether the mounds of data that apps routinely gather could help doctors make better decisions about women’s health — and maybe even spare patients from invasive fertility-related medical monitoring (1).
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As we mentioned, one of the apps was Kindara, which is largely used in the United States by those trying to conceive (TTC) or trying to avoid pregnancy (TTA), and the other was Sympto, which is mainly used as birth control overseas. Both rely on the highly accurate Symptothermal Method of tracking fertility (1). (If you’re new to this method, brush up on it here.)
The research team then drew on a pool of de-identified data from the two apps. De-identified means that names or other kinds of personal information were stripped from the data before it was handed over to researchers. The resulting dataset was massive, including more than 30 million days of observations from over 2.7 million menstrual cycles (1).
Overall, the study found that self-tracking the menstrual cycle and fertility-related body signs was a reliable method to either get pregnant or avoid pregnancy. This confirmed results from a smaller study that showed the likelihood of pregnancy rose 12–20% per cycle when using an app and tracked one or more fertility signs (basal body temperature (BBT), cervical mucus (CM), cervical position, and/or urine luteinizing hormone (1).
The Nature paper also found the average length and range of the follicular phase, the first phase of the menstrual cycle that ends at ovulation, was a bit broader than previously reported. The study showed the vast majority of ovulations occurred sometime between days 10 and 24 — a big range. Just 24% of ovulations occurred on cycle days 14 and 15 — the days that people once believed were the prime ovulation days (1).
(Side note: An earlier study also found ovulation happens sometime between days 11 and 21, a slightly smaller, but still sizable, window of time (3).)
As for the length of the luteal phase (the phase after ovulation), about 35% of cycles had a luteal phase lasting 12–13 days. Around 20% of cycles had a luteal phase lasting just 10 days or less (1). A short luteal phase can make it more difficult to conceive or maintain a pregnancy. Find out about trouble-shooting a short luteal phase here. (4)
The research also showed a clear shift of about 0.7 degrees Fahrenheit (0.36 Celsius) in BBT before and after ovulation. App users reported greater amounts of stretchy CM in the days leading up to ovulation, which is to be expected since CM is a fertility sign (1).
Why evidence like this matters
This new science is pretty heartening because so many of us nowadays diligently, yet there’s very little research on these apps that we’ve come to depend upon. Many of the studies that do exist were conducted by, or paid for, by the companies that own fertility apps, which may raise concerns about bias (1).
Plus, the new research underscores how the scientific world is finally taking menstruation and fertility seriously. Or, as Laura Symul, a Stanford University scientist and one of the study authors told Kindara, “these apps are kind of a new microscope for the menstrual cycle. Their digital nature makes them easier to analyze and provides us with new ways to evaluate aspects of the menstrual cycle and fertility (1).”
At the same time, the research also helps healthcare practitioners, who may be new to the world of fertility apps, to understand the evolving potential of technology-based self-monitoring in health and wellness (1).
As fertility apps continue to yield a vast trove of valuable information on women’s health, the technology one day may even supplant more traditional monitoring methods, such as ultrasounds and hormone tests, in keeping tabs — safely and less invasively — on your health (1).