You will get the living hell spammed out of you for years if you apply for this magazine (which is always free, there is no such thing as a paid subscription to American Baby). Of all of the specialized groups of addresses for which junkmailers pay a premium, the two most prized are expecting parents, and, especially, first-time expecting parents, since they tend to spend money at an alarming rate.
If you don't mind junk mail, go ahead and subscribe. Just know what you are getting, which isn't a freebie of a normally paid periodical. This magazine exists as a means to harvest names and addresses of expecting parents for profit. It is also loaded with advertising, no surprise there. The articles are mostly recycled. They ask for your due date, so that you get the entire "series" of articles, but everyone generally gets the same stuff at the same stage of the baby's development.