How do you track your cycle, and why does it matter?
How do you track your cycle, and why does it matter?
For years, hormonal birth control methods were the golden standard for managing periods and fertility; the pill, the patch, the IUD, and everything in between.
Nowadays, people with periods are diving deeper, asking critical questions about the side effects of these hormonal contraceptive methods and wanting to get to know their bodies better. Non-hormonal contraceptive options are gaining popularity, partially thanks to the explosive growth of period and fertility tracking apps.
These apps offer insight into physical and mental health, but they also come with their own set of risks. Since September, Yoni has joined research led by Tamara Thuis and Maria Carmen Punzi at VU Amsterdam to investigate how these apps can be developed and used responsibly. It’s high time to dive into the world of period and fertility tracking apps. So, let’s discuss exactly what they do, their pros and cons, and delve into the ongoing research Yoni is participating in.
Period and fertility tracking apps: what do they do?
Let’s start at the beginning: what exactly are period tracking apps, anyway? Commonly known as menstrual-, fertility-, Fem Tech-, or cycle tracking apps, they help you keep track of your menstrual cycle: when and how long you have your period, how you feel, and whether you experience symptoms such as abdominal pain or mood changes. You enter this information, and based on this data, the app makes predictions about your next period, ovulation, and fertile period. Some apps also allow you to track biomarkers such as your temperature or cervical mucus, which are linked to your monthly fertile window.
Pros and cons
Period tracking apps have been popular for quite some time, because they allow you to store all symptoms and menstruating days in one place and permit you to gain insights into your body and health patterns. But recently, more menstruating people are relying on these apps specifically for birth control. In 2024, for example, 1 in 10 young women (aged 18-29) in the Netherlands relied on an app as a method of contraception (Rutgers, 2025). Yet, many of these apps are not cleared to be used as birth control, particularly because it is extremely difficult to predict ovulation.
It’s because of the latter that medical professionals and researchers treat period and fertility tracking apps with reservation, and at times criticize them. While the apps give people a renewed sense of autonomy over their bodies, there is a risk that users place complete trust in the apps’ predictions.
Especially on social media, influencers are spreading exaggerated and unnuanced statements about the negative side effects of hormones. With hashtags like #naturalcycle, they promote to “get off the pill” and start tracking their cycle instead. Health experts are concerned that the online portrayal of period tracking apps as a reliable contraceptive method leads to more menstruating people distrusting hormonal contraception methods. In the Netherlands, the number of abortions has risen by 27% since 2021, prompting doctors to warn of the consequences that replacing hormonal contraception with apps can have. While there is no clear evidence that the rising number of abortions is due to the use of these apps (Rutgers, 2025 and Cetera, Punzi, Boero, 2025), it is clear that the apps should be used responsibly to optimally benefit from them.
Transparency, responsibility, and privacy
As more people use tracking apps for understanding their cycles, it becomes more important for people to be informed of how to use them responsibly.
But, beyond the responsibility of the users, there is also a responsibility by the companies behind the apps. The algorithms used by the apps can be a “black box”, where users cannot follow how they work and how their data is processed. What many users may not realize is that the predictions shown to them are often based on averages, patterns, and probabilities rather than on the user’s unique cycle. If the user’s period or experiences deviate from the algorithmic standard, predictions may be less likely to be accurate. In addition, there is much debate about the quality and origin of the data on which the algorithms for apps are based: they may be incomplete, unreliable, or biased. As a result, social taboos about sex, menstruation, or contraception may be incorporated into the algorithms. All of this further goes to show that there are risks of major, unintended consequences if you rely solely on period tracking apps.
In addition, there have also been concerns about the privacy of user data. In 2019, the period tracking app Flo made headlines because it shared intimate information about pregnancy planning with platforms like Google and Facebook, resulting in targeted marketing for users. Privacy advocates also worry that in some cases, this data could be potentially used for the prosecution of abortion-seekers in countries where abortion is illegal.
Fortunately, this is not (yet) an issue in Europe, but the underlying risks associated with menstrual tracking apps certainly need to be understood and addressed. While experts and the media tend to focus on user responsibility, encouraging users to be hyper-aware of health and privacy risks, we believe that the spotlight should also be on the organizations themselves. These organizations have a duty to act responsibly when developing apps that millions of women trust with their personal and private data.
Yoni x Research
Therefore, Yoni is participating in the Responsible AI in FemTech Apps research project in collaboration with VU Amsterdam. Led by researchers Maria Carmen Punzi and Tamara Thuis, we will be looking at how AI can be used responsibly in menstrual and fertility tracking apps. Alongside partners 28X and the Feminist Generative AI Lab, we will be delving deeper into this topic in the coming months. We’ll keep you updated, so stay tuned!
