Target keeps close tabs on everything its customers buy. They tag their customers with guest IDs and store all the detailed information they get from each customer. They then analyze the information and track it. They’ve become so accurate at tracking that they’ve been able to predict with extreme accuracy when women become pregnant. 

Target has created a system that allows them to send coupons for expecting mothers. They have an algorythm that includes 25 very specific products. When a person buys those products, they can predict a pregnancy with decent confidence. What’s even scarier is that they can even guess when the person’s going to be due based on what they buy!

What they’ve found is that they freak out their customers by congratulating them on their pregnancies before the customer has formally set up any registry or anything with Target, or even told their own family! 

A father in Minneapolis went to a local Target demanding to speak with a manager. He was livid that his daughter had received coupons and information on maternity clothing and baby items. It was inappropriate for Target to be sending his daughter, who was still in high school, information like that promoting pregnancy. 

Later, the manager called the father to apologize again and was told that the father had spoken to his daughter. She admitted that she was pregnant and due in August, so the father apologized to the manager. 

(Source)