This may not be exactly what you were asking for but The Sons 'Verse by zooeyrye is amazing, and while the focus isn't on the pregnancy Dean is the one pregnant

http://community.livejournal.com/deancastiel/743148.html

I HIGHLY recomend this awesome well done fic too!!

Also she has a new fic called: Given Enough, that I believe deals will mpeg with dean as the pregnant with cas and his kid as well http://community.livejournal.com/foolish_times/46760.html ch 1
http://community.livejournal.com/foolish_times/46946.html#cutid1 ch 2

so far she has written 2 chapters and its wip.

FayJay's Babbydaddy series is fun. Dean is only pregnant in the first series though. http://archiveofourown.org/works/4677

There is the Shmoop Verse by Mary Higgins
http://anne-higgins.livejournal.com/12295.html
sequel http://anne-higgins.livejournal.com/12936.html
It lovely and well, shmoopy as hell! 8D
Dean is the one pregnant and while it's in the beginning, she promised us more of it!
;D

Winged Golden Tiger

ooh those are what made me start the search actually, thanks though :)

ah there is also:
No Room at the Inn
http://www.sparklydanceboys.com/epeeblade/supernatural/inn.html
Touched by an Angel
http://mckays-girl.livejournal.com/93057.html

Voila!

thank those are really cute, i love the christmas one.

I really like Mpreg and even went to search for it in all my favorites ( and God but I have many...)
Here it is
Infinite Chances by ScarletFBL
http://scarletfbl.livejournal.com/72147.html#cutid1
Hope you like!

Winged Golden Tiger

aww that was adorable and brillant thankyou