One in Five U.S. Women Already Use Flo. Now the 420-Million-User App Is Building Infrastructure for the Future of Digital Health

The world’s most popular women’s health app is investing in regulatory-ready foundations for advanced health features.

A Startup That Reaches More Women Than Most Hospital Systems

Flo Health has achieved something rare in digital health: genuine scale. The women’s health app now serves over 420 million users globally, making it the world’s leading FemTech application. In the United States and United Kingdom, approximately 20% of women in the app’s core demographic—roughly one in five—actively use Flo. It holds the distinction of being the number one OB-GYN recommended app and was named one of Time Magazine’s Best Innovations of the Year.

Now, the company is taking its next step: building the compliance infrastructure that positions it for the future of digital health. The move represents a significant investment for a consumer health app—establishing the foundations that could support increasingly sophisticated health capabilities as the industry evolves.

From Wellness Content to Enhanced Health Features

Flo began as something like a digital health book. The company invested in medical safety and accuracy from day one, establishing a medical board to oversee feature development and hiring in-house doctors. But the core product delivered health insights and information—helpful content that served users well.

The company’s Chief Technology Officer, Roman, who has spent over eight years helping grow Flo to unicorn status, described the evolution. As the company progresses and adds more features, the team sees a need to go deeper into health and wellness. The goal is to deliver more sophisticated capabilities—symptom evaluations, risk assessments, and health insights that go beyond general information.

The ambition is comprehensive: to be an essential health partner for women throughout their entire lives, from early reproductive years through perimenopause and menopause. That vision benefits from building robust compliance infrastructure now.

AI at the Core

Artificial intelligence already powers key functionality within Flo. Machine learning models predict cycle lengths and how individual cycles will unfold—one of the app’s core features that users rely on daily. But AI extends beyond the product itself.

Simas, Flo’s Director of Engineering, who previously served as Director of Software as a Medical Device at AstraZeneca, explained that AI is embedded in the company’s operations. Engineers use AI to write code and documentation. The company employs AI for content generation and content review. It functions as a productivity enhancement tool across the organization.

This dual role—AI in the product and AI in the workflow—creates both opportunity and complexity as the company builds more sophisticated health features. The team must maintain the agility and speed that defined their growth while establishing the documentation and quality processes that advanced health capabilities require.

The Scale of Operations

Understanding Flo’s infrastructure investment requires understanding the company’s operating pace. The engineering team runs approximately 400 concurrent A/B tests at any given time. Over the course of a year, they execute more than 1,000 A/B tests. The company releases software daily.

Roman leads a global engineering, data science, and security organization of 200+ people. Under his leadership—Roman is a three-time CTO who previously led engineering at Pay For Later before its acquisition by Amazon—the team has scaled systems to support hundreds of millions of users and delivered features like Anonymous Mode.

The company competes directly with Apple Health for features like cycle tracking. Competing against one of the world’s largest technology companies as a relatively minor organization requires moving fast and working smart. That context made the prospect of introducing a Quality Management System feel risky—would it slow down the innovation engine?

Building a Flexible Architecture

The architectural approach Flo chose reflects sophisticated thinking about where enhanced quality processes add value. Rather than placing the entire app under QMS—which would have created an unnecessary burden on features that don’t require it—the team designed a modular approach.

Some portions of the app operate under QMS and enhanced oversight. Others remain outside. The community feature, a social function that allows users to communicate with each other, doesn’t require the same level of process rigor. More sophisticated health features under development do benefit from that structure.

This approach allows engineers working on standard features to continue operating at full speed with minimal additional process, while teams building advanced health capabilities follow appropriate compliance workflows. Timothy, Flo’s Chief Legal and Compliance Officer, who has spent over eight years at the company and oversees compliance across global operations in the United States, UK, Netherlands, Cyprus, and Lithuania, emphasized that many organizations get this wrong. They put everything under QMS without differentiating between different types of features, slowing down the entire organization unnecessarily.

From Intent to Implementation in Under 90 Days

Working with compliance partner Ketryx, Flo built its regulatory-ready infrastructure in approximately 87 days—roughly 12 weeks from deciding to invest in this capability to having a live QMS and the ability to produce, review, and approve documentation through robust compliance workflows.

The speed came from automation. The team integrated their compliance tooling with CI/CD pipelines, automatically capturing build, test, and deployment evidence. Traceability matrices are generated directly from source systems. Risk analysis and threat modeling are executed as part of standard development workflows rather than as separate compliance exercises.

The result, according to Roman, is that day-to-day engineering work has changed very little. The company operates with the same speed and agility as before, but now with stronger foundations in place. Simas offered that engineers working within the quality management system may have actually gotten faster, motivated by the significance of building more sophisticated health capabilities.

A Global Health Mission

Flo Health’s reach extends beyond paying subscribers in developed markets. The app is available free of charge in many countries, including India, Ukraine, and across Africa. The company is the number one health and fitness app in India.

This reflects a broader philosophy. As Roman explained, the company believes in building a better future for female health worldwide, not just in the UK and the US. The decision to provide free access in countries where users may lack the financial means for a subscription represents an investment in global health education and women’s empowerment.

That mission now includes building the infrastructure to support increasingly advanced health capabilities. A $200 million funding round led by General Atlantic provides resources for the investment. The company has demonstrated that building regulatory-ready foundations doesn’t require sacrificing pace—they did it in under 90 days while maintaining their innovation velocity.

What This Means for Digital Health

Flo’s infrastructure investment signals a maturation of the digital health space. Consumer health apps that achieved scale through user experience and engagement are now building the foundations that could support more sophisticated health features as the industry evolves and regulations develop.

The company already holds ISO compliance for privacy and security. Adding QMS infrastructure extends that foundation. For the one in five American women already using the app, this investment means the company is positioning itself to deliver increasingly valuable health insights through an interface they already trust and use daily.

Roman’s framing positions compliance infrastructure as a competitive advantage rather than a burden. If a company can move faster than competitors while maintaining strong quality processes, it gains significant advantages. The infrastructure Flo built in 87 days isn’t just about compliance—it’s about maintaining the speed that made the company successful while building foundations for future possibilities.

For 420 million users worldwide, this evolution represents Flo’s commitment to their health journey. The company that helped them track cycles and understand reproductive health is now investing in the infrastructure to deliver even more value—and doing so without asking them to slow down or change how they use the product they already trust.

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