Duplicate Content Issue

Hi,

Can anyone tell me why the following two URLs are returning the same content? (there is no 301 redirect going on)

http://www.babyssentials.com/first-9/basics/how-much-weight-should-you-gain-during-pregnancy/

http://www.babyssentials.com/first-9/how-much-weight-should-you-gain-during-pregnancy/

(shouldn’t the second one 404?)

Thanks!

-Jeremy