Rick Bowmer, AP
A Target sign is shown on the front of a Target Store Tuesday, May 17, 2011, in Wilsonville, Ore.

Using ceded personal information, like a credit card number, Target is able to model a shopper's characteristics close enough to predict whether or not they are pregnant, and if so, what trimester they are in.

New parents are a retailer's holy grail, said Andrew Pole, a statistician hired by Target, in an interview with Charles Duhigg in a New Tork Times Magazine article.

Because Target sells everything from baby supplies to electronics, a goal for the company has been to convince customers to shop for most everything at its stores.

And the retailer has a chance to rope customers in around the birth of a child, when parents are so overwhelmed they are open to a one-stop shop. Natal ads from Target are aimed at women in their second trimester, the article reports, as that is when most mothers begin the rush for baby supplies.

According to the New York Times Magazine, Target assigns each shopper a unique Guest ID number. There are about 25 products that, when taken together and analyzed, will assign each shopper a “pregnancy prediction” score.

“We’re living through a golden age of behavioral research. It’s amazing how much we can figure out about how people think now,” said Eric Siegel, a consultant and the chairman of Predictive Analytics World, told the New York Times Magazine.

"Well, if Target can use statistical relations to predict pregnancy, I'll bet they can predict other things too. For example, the early stages of Alzheimer's," said Kevin Drum, a writer at Mother Jones.

Drum is concerned this information could be sold to companies wanting to take advantage of the less competent.

The Wall Street Journal reports that Google and other advertising companies have been bypassing the privacy settings of the Safari Web browser to track Internet habits.

"The companies use special computer code that tricks Apple's Safari Web-browsing software into letting them monitor many users," reported the Wall Street Joural.

Google removed the code when The Wall Street Journal contacted them.

The Atlantic reported that the news sites which use ad targeting the most include The New York Times, Yahoo and CNN.