When Yeeun Jo, a student at University of Illinois at Urbana-Champaign (UIUC) contacted me in 2025 to ask about data tracking in app advertisements related to women's health and pregnancy I was a bit skeptical. I think I first told her along the lines that while such data collection was broad it was rarely so specific as the advertisers were unlikely to act on specific information like which week of pregnancy a woman was currently in.

Not to mention, Facebook’s historic $5 billion FTC fine for deceptive third-party data tracking, and the FTC’s subsequent 2021 crack-down specifically targeting Flo Health for passing intimate logging metrics to Facebook's SDK. I thought it was unlikely they'd find much.

10 years of ad experience, and I'm still wrong on what ends up tracked

Well, it's a year later and Yeeun was 100% correct in her guess that mobile apps and mobile ad networks were still tracking more data than I expected. She and Brad Reaves released their paper "Expecting (Targeted Ads)? Network Analysis of User Health Data Leakage in Fertility Tracking Apps" showing the high specificity which these events are tracked...

Rest of my blog post & AppGoblin links to the apps mentioned in Jo & Reaves paper: https://jamesoclaire.com/2026/06/30/the-pregnancy-and-health...