i've read a few mangas where pregnancy occurs, (weather it's the main character or a friend of his) here are a few i read and like
17 sai no mama (still icomplete though)
kami-sama no orgel (incomplete as well, 1 volume out only)
ichigo no gaku
there are more where the pregnancy occurs near the end, i'm not gona list the titles cos it's gona be a spoiler
anw, some people think that it's not "healthy" to present pregnancies in manga as some of them removes the seriousness of the subject (for example, teen pregnancy in akkan baby is turned into a comedy)...for me, i kinda likes the stories in the manga, it's a nice twist of events and it changes from the usual "fall in love - third wheel appears - break up - patch up - together forever" deal
what do you think?