Well, with the male body being ill-equipped to host a pregnancy, it would likely become a foreign mass, and eventually a tumor that would need removal as his body continues to reject the foreign material.
@BeannachtOraibh That's just the movies, though. ;) In the books, everything changes, including the voice (remember, Harry and Ron could hear the changes in their voices when they first transformed, and this remained true even in the seventh book), so this question could still be valid. But I'm just nitpicking. 😂 Great analysis, by the way! 😉