Stardust shared sensitive period tracking data with third-party analytics firms, according to new privacy research from Mozilla.

The findings expose a privacy divide in femtech, where users often trust apps with highly sensitive reproductive health information.

The research was carried out by Mozilla’s Privacy Not Included team, which tested several period tracking apps.

It found that Stardust, a period tracker used by millions, shared users’ reproductive health data with analytics companies, a practice the research said contrasted with its privacy-first marketing.

Analytics companies collect and examine information about how people use digital products, often to help businesses understand user behaviour or improve marketing.

The findings raise questions about whether privacy promises made by health apps match what happens to users’ data.

According to research reported by TechCrunch, one other period tracking app tested by Mozilla received what researchers called a “squeaky clean” rating, suggesting similar services can operate without sharing sensitive health data in the same way.

Period tracking apps have come under greater scrutiny in the US since the 2022 overturning of Roe v Wade, which removed federal constitutional protection for abortion.

Some users and privacy advocates have warned that menstrual and reproductive health data could potentially be sought in legal cases.

The research also points to a broader regulatory problem for consumer health apps.

In the US, many health apps are not covered by HIPAA, the health privacy law that applies to medical providers and some healthcare organisations.

That means some consumer apps may be able to collect, share or monetise sensitive health data under rules that differ from traditional healthcare privacy protections.

The femtech market, estimated in the report at US$50bn, has grown quickly, but privacy regulation has not always kept pace with app development.

Stardust had not publicly responded to Mozilla’s findings at the time of the original report, and its privacy policy remained live on its website.

The issue is particularly sensitive for period tracking because the data can reveal patterns around fertility, pregnancy, contraception and reproductive health.

Mozilla’s wider Privacy Not Included initiative has examined consumer technology products for privacy and security concerns since launching in 2017, including connected devices, children’s toys and health apps.

The findings come as US lawmakers continue to debate stronger federal privacy rules for sensitive health information collected by consumer apps.

The American Data Privacy and Protection Act, which has been stalled in Congress since 2023, includes provisions addressing sensitive health information collected by consumer apps.

Experts have also warned that anonymised health data can sometimes be re-identified when combined with other information, such as location data.

Re-identification means linking supposedly anonymous data back to a specific person.

A 2019 study found that menstrual cycle data combined with location information could identify individual users with high accuracy.

State-level privacy laws in places such as California, Virginia and Colorado have also given consumers new rights around personal data, although enforcement can vary.

Privacy advocates say the research underlines the need for clearer data practices, stronger safeguards and greater transparency in femtech.

For users, the findings are a reminder that health apps do not automatically protect health information in the same way as healthcare providers.

The report suggests period tracker companies that put privacy first may be better placed to build trust in a market where long-term use depends on confidence.

Mozilla’s investigation suggests privacy promises in femtech do not always match practice, and that period trackers can function without sharing sensitive user data in the same way.

Juno Bio has secured US$3.8m to expand its diagnostics platform for vaginal health and reproductive care.

The funding round was led by Ada Ventures, with participation from Artesian, Entrepreneur First and Illumina Accelerator.

The women’s health startup said the seed funding will support the launch of its first CLIA-certified sequencing laboratory in Oakland, California, and a new clinical vaginal microbiome and STI test for healthcare providers.

CLIA certification refers to US laboratory standards for testing human samples used in diagnosis, prevention or treatment decisions.

Dr Leighton Turner, co-founder and chief scientific officer of Juno Bio, said: “The vaginal microbiome is still one of the least understood systems in the body at a clinical scale.

“With our lab, we’re starting to build a measurement standard that clinicians can actually use.

“We believe the level of detail from this kind of testing can meaningfully improve how vaginal healthcare is provided.”

The company is developing precision diagnostics for vaginal health, where patients can experience recurring symptoms, inconsistent diagnoses and treatments based on trial and error.

Juno Bio said bringing testing in-house gives it greater control over the process, from sample handling to results, while allowing it to refine its technology and build what it says is one of the largest datasets focused on the vaginal microbiome.

The vaginal microbiome is the community of bacteria and fungi that naturally live in the vagina. Changes in this balance can be linked to infections, symptoms and wider reproductive health issues.

Juno Bio’s newly launched clinical test examines the wider vaginal microbiome and screens for four common sexually transmitted infections, or STIs.

Rather than looking for a single cause, the test is intended to give clinicians a broader picture of what may be contributing to symptoms.

Juno Bio says this matters because multiple infections can occur at the same time and microbiome changes may be linked to fertility, menopause or recurrent infections.

Dr Anna Powell of Johns Hopkins said: “Vaginal microbiome testing has the potential to significantly reshape how we understand and manage vaginal health, particularly for patients with recurrent or unexplained symptoms.

“While the field is still evolving, advances in sequencing and data interpretation are moving us closer to a future where more personalised, microbiome-informed care can complement existing diagnostic approaches.”

Check Warner, co-founding partner at Ada Ventures, added: “Juno Bio is setting a new standard for how vaginal health is understood and managed.

“What they’ve built at this stage, with this level of capital efficiency, is exceptional.

“We’re proud to support the team as they scale their clinical infrastructure and continue leading innovation in this critically underserved category.”

Black women in the UK want clearer, more accessible breast cancer screening information, research has found.

The study looked at why Black African and Black Caribbean women are less likely than white women to attend breast screening.

Researchers at the University of Surrey held focus groups and interviews with 47 Black African and Black Caribbean women aged 50 to 71.

Women in this age group are routinely invited for NHS breast screening.

The researchers said only 45 per cent of Black women attend screening, compared with 63 per cent of white women.

Anietie Aliu, lead author, postgraduate researcher at the University of Surrey and registered nurse, said: “Diagnosing breast cancer early can dramatically improve a person’s chance of survival.

“Breast cancer screening plays an important role in this by identifying the cancer and ensuring a person receives speedy treatment.

“Despite the importance of screening, Black women are less likely to attend appointments than white females.

“This puts them at risk of a potential cancer being diagnosed late and spreading to other areas of the body. We need to understand what is preventing Black women from attending these appointments and help identify ways to remove such barriers.”

The study found a need to increase awareness of breast cancer screening, especially among women less familiar with the service.

Some women, particularly those born outside the UK, knew little about breast screening before receiving their first invitation.

Others questioned why they needed screening when they had no symptoms.

The importance of trusted conversations was also identified.

Researchers found that some Black women expected their GPs to speak to them about breast screening, particularly before they reached screening age.

Although NHS breast screening is organised through national screening services, researchers said GPs often have established relationships with patients and may be well placed to offer brief advice on preventive care, including breast screening.

Participants called for stronger links between GP practices, breast screening services and Black community champions.

They said this could help women receive trusted information, ask questions and feel reassured.

Faith and religious beliefs also shaped decisions for some women.

Some Black African Christian women said illness, including cancer, was not permitted by God in their bodies, while others saw screening as a personal choice that did not conflict with Christian faith.

Muslim women highlighted the importance of being able to state their religion on medical appointment forms to help ensure they were seen by a female mammographer.

A mammographer is a healthcare professional trained to carry out breast screening scans.

Aliu added: “Breast screening can save lives, but our findings show that attendance is shaped by multiple factors, not just awareness, although awareness remains important.

“Women need relatable screening information, reassurance, flexible appointments and services that are accessible within their communities.

“Many felt that invitation letters were too formal, and that leaflets and media imagery did not reflect them, making it harder to relate to screening.”

Dr Afrodita Marcu, senior research fellow at the University of Surrey and member of the research team, said: “We need a more collaborative approach, where primary care, screening services and community voices work together to support women before, during and after the invitation.”

The researchers said future breast screening interventions should be designed with Black women, rather than for them.

They said user-friendly and culturally relevant resources, developed with communities, healthcare professionals and screening services, could improve understanding, reduce fear and make breast screening feel more accessible and reassuring.

Dr Robert Kerrison, associate professor of cancer care at the University of Surrey, said: “There is no question that breast screening can be lifesaving, but we need to make it easier for women to understand, access and feel reassured by the programme.

“This means improving communication, addressing practical barriers and making sure healthcare professionals and community partners are supported to provide clear and trusted information.”

The team has also explored healthcare professionals’ perspectives and worked with stakeholders to develop user-friendly materials with Black women.

Researchers said this co-designed approach could help ensure breast screening messages are culturally relevant, practical and shaped by the people they are intended to support.