There is a way to enable males to become pregnant and carry children, but that depends on the type of mod you want. I have seen woohoo mods at several sites advertising that feature, but they usually involve a style that you prefer to play. You can look at the mods in Sims 3 at
MTS - Sims 3.
You should also try Google to find Sims 3 woohoo mods using those keywords to see if other sites have them as well.
I personally use Twoftmama's woohoo mod in combination with Twallan's Super Computer mod to pollinate or impregnate males when I chose to if the male is living on his own. But keep in mind that the males themselves do not have meshes to show pregnancy or have clothes to accommodate those pregnancies. That is another search for separate mods to enable them to look and be pregnant.