In our economy, the devices we use are constantly asking us to share — or sometimes just taking — our data. And when it comes to that data, not much of it is more personal and private than our health. Yet personal health devices and apps are a growing industry, a subset of which is targeted specifically at women. It’s called femtech, and it includes devices like FitBit, the Ava fertility bracelet, and the Eve by Glow period tracker. Yet sharing your data also means that data can be used to target ads in ultra-precise ways, as Molly McHugh at The Ringer reports. Marketplace host Kai Ryssdal spoke to McHugh about the femtech industry and her own experiences with advertisers who knew more about her than she realized.

Click the audio player above to hear the interview.