Data Transparency and Control in Fertility Tracking
What the study did (in a nutshell)
Revealed hidden data flows: Real-time tracking showed sensitive data was shared with third parties across multiple countries, often without user awareness.
Unpacked user concerns: We showed that willingness to share data is contextual and depends on various factors. Survey participants were willing to share data for public good, but opposed commercial use, even if anonymised.
Co-designed solutions: Developed 10 actionable design ideas with users to improve transparency and control in fertility apps.
Intro
Fertility tracking apps are marketed as empowering tools for health and wellbeing. But our findings reveal a more troubling reality. Empirical analysis of real-world data transmissions from fertility tracking apps suggests that highly sensitive data is routinely transmitted to commercial third parties, often without users’ knowledge or consent. We combined technical analysis, user surveys, and co-design workshops to examine how fertility tracking apps handle intimate data. They found widespread data-sharing practices and a stark mismatch between what users expect and what apps actually do.
Intimate moments, invisible transmissions
We first monitored the data flows of eight popular fertility apps and devices. Simply logging a period, measuring temperature, or syncing a device was enough to trigger real-time transmissions to a wide network of IP addresses.
On average, fertility trackers communicated with over 13 companies across 7 to 8 countries. One app contacted 26 different organisations in 12 countries, including jurisdictions with weak or unclear data protections. These transmissions often occurred during the most sensitive moments of use, such as when entering data on menstruation, sex, or hormone levels.
Factors influencing willingness to share
“ Maybe someone knows my menstruation period, but it’s not that important to me.”
In a survey of 162 fertility tracker users, we found that users were generally willing to share data when it served a medical or societal benefit, for example with doctors or academic researchers. However, there was strong discomfort with sharing data with advertisers, insurers, or social media companies, even if de-identified. Participants also raised concerns about profiling, surveillance, and the broader imbalance of power between users and app developers.
Gender gaps and reproductive justice
“Fertility apps could be used to regulate women’s bodies after Roe v. Wade and threaten bodily autonomy”
Beyond privacy, we highlighted how fertility apps reflect and reinforce broader gender asymmetries. Many users pointed out that while women’s bodies are heavily tracked, health research gaps persist, especially around conditions like PCOS. These reflections link concerns about data use to broader issues of reproductive justice and design ethics.
Designing better fertility trackers
“I feel like putting responsibility on the user is not bad per se, but the app also has a duty to inform us clearly.”
Rather than stopping at critique, we worked with users to co-design ten concrete mechanisms for transparency and control, readily implementable by designers. These mechanisms span the full user journey, from app store listing and onboarding, to daily use and data deletion. Users expressed interest in data donation, but only if it was offered with meaningful consent, the ability to opt in, and the option to withdraw or delete data after use.
Regulation, design, and user empowerment
“There should be more laws protecting consumers from having to constantly protect themselves.”
Our work also speaks to broader challenges around digital responsibility. Users are expected to micromanage their data, but we need to put responsibility, we argue, on developers, platforms, and regulators.
Therefore, we emphasise the need for stronger accountability, improved regulatory enforcement, and design approaches that centre user agency, particularly when it comes to intimate health data.
Publications
Hudig, A.I. & Singh, J. (2025). Intimate Data Sharing: Enhancing Transparency and Control in Fertility Tracking, CHI Conference on Human Factors in Computing Systems (CHI ’25), Yokohama, Japan, https://doi.org/10.1145/3706598.3714089.
Talks
PubTalk: AI&Equality (online). Watch here: https://aiequalitytoolbox.com/library/data-sharing-transparency-and-control-in-fertility-tracking/