In my family’s case, my wife’s hospital admission and prescription was sufficient to correctly identify her as likely 10-12 weeks pregnant. Their confidence in that was sufficient to yield us a Fedex’d box containing congratulations and starter kits of enfamil, on her due date. Since they don’t read your records, just infer from events, they didn’t know that she had miscarried, and nearly died in the process.
I know this, because Enfamil identified the list used to target her, and I bought it for my zip code. I also learned that my neighbor 4 doors down has type 2 diabetes, and has expressed interest in a BMW or Audi at the end of her then-current lease. (She went Audi btw)
When people lecture you about various observational biases, you’re being paranoid, etc, they are full of shit. The marketing machine is way more wired up into everyday life than you can imagine.