[soyandtophu]

It looks like there's a really cute mpreg manga over in the art gallery, but another with implied mpreg would be Sex Pistols (which also goes by the name of Love Pistols). It doesn't show much, a few panels where you think you might see a little something, but it could just be the way that the folds of their clothes are. There's also a panel, but I'm not sure in which volume/chapter, which shows one of the couples going through the process of their baby up until the arrival.

There's also this, which just shows a list of manga that has or implies mpreg within their story.