What does it mean to be certified as a "fertility monitoring system"?

The inne mini lab is CE-marked as an in-vitro diagnostics medical device for self-testing with the intended use of detecting changes in progesterone (in saliva) across a woman's menstrual cycle. By monitoring changes in progesterone across the menstrual cycle, the inne mini lab is able to identify a woman's fertile window (based on ovulation prediction and confirmation), but also luteal and follicular phases.