Apps used to track menstrual cycles, monitoring periods and fertility windows, are not as reliable as users may think, according to research from Rotterdam School of Management Erasmus University (RSM).

Such services, according to researchers Maria Carmen Punzi and Tamara Thuis, may compromise user privacy and reproductive autonomy as users are subject to data breaches, and exposed to limited or biased information about their reproductive health.

Many period tracking apps collect extensive personal health data, including intimate details about users’ sexual activity, menstrual symptoms and reproductive health. The research identified concerning gaps in data protection, with some apps sharing sensitive information with third parties, including advertisers, often without user informed consent.

The study’s mapping revealed that many algorithms used by such apps are trained on limited datasets that may not represent the full diversity of menstrual experiences across different demographics, ages and health conditions. This, the researchers warn, can lead to inaccurate predictions that disproportionately affect certain user groups, potentially impacting contraceptive and related health decisions.

Users frequently lack clear understanding of how their data are being used, stored and shared. The study’s mapping shows privacy policies are often complex and fail to communicate adequately the risks associated with data sharing, particularly in jurisdictions with restrictive reproductive health policies.

The research highlighted concerns about the medicalisation of normal bodily functions and the promotion of constant self-monitoring, which may create anxiety and reinforce narrow definitions of what’s normal. Menstrual cycles change with age, with stress or through pregnancy. Natural variations can be interpreted as abnormalities by the apps, and these interpretations can cause uncertainty for the user.

The researchers say their work comes at a critical time when reproductive health data privacy has become increasingly important due to changing legal landscapes around reproductive rights.

“We live in a time when reproductive rights are at risk and women are increasingly looking for alternatives to hormonal birth control,” said the researchers. “It is essential that we pay attention to the ethical development and implementation of innovation when it applies to contraception. The influence of algorithms on users’ experience of their menstrual cycle and fertility is sometimes invisible but can still change behaviour related to it.”

The findings suggest that while these technologies can provide valuable health insights, significant ethical frameworks and regulatory oversight are needed to protect users better. The researchers have made three main recommendations.

• Individual app users need clear education about limitations and risks of these technologies
• Organisations – such as companies developing these technologies – must scrutinise their products for biases, and be transparent about the way the data are used
• Society should challenge the taboos and biases around menstruation that influence product development and user experiences.

The research from RSM (www.rsm.nl) was published in Contraception (www.contraceptionjournal.org), a journal in contraception and family planning published by Elsevier. The article can be found at www.contraceptionjournal.org/action/showPdf?pii=S0010-7824%2825%2900028-9.