I didn't look at all of them, but I'm not all that puzzled by these. People in advertising could probably make good use of a lot of these given enough creative juice. My personal experience is that it often happens the other way around. The ad guy gets an idea or concept and commissions the photo. I guess photographers here are trying to come up with ideas in anticipation of that 'great idea'. I suspect it's cheaper to just buy the rights to a stock photo than create the whole photo shoot.
Just off the top of my head, for the first pic, Barbara Kruger did something sort of similar:
http://books.google.com/books?id=JJNkVs2Nxm4C&pg=PA105&lpg=PA105&dq=barbara+kruger+pregnant+man&source=bl&ots=MLKVzEdjh_&sig=0GuyEd_mRa8p3QNTb1LC4Yps8ec&hl=en&ei=9GGTTYGbB-a_0QGE5NnMBw&sa=X&oi=book_result&ct=result&resnum=2&ved=0CBcQ6AEwAQ#v=onepage&q=barbara%20kruger%20pregnant%20man&f=false
Sorry, that's the only place I could find the images and they're a bit tough to read. Her men aren't visibly pregnant but idea is still the same.
Anyway, yeah, odd but I'd not call the unusable!