Are you sure about that?

https://www.forbes.com/sites/kashmirhill/2012/02/16/how-targ...

"As [Target's] computers crawled through the data, he was able to identify about 25 products that, when analyzed together, allowed him to assign each shopper a “pregnancy prediction” score. More important, he could also estimate her due date to within a small window, so Target could send coupons timed to very specific stages of her pregnancy"

Read the entire article for a more horrifying anecdote.