The biggest trouble with pregnancies is the amount of branches it creates. As soon as a pregnancy starts to show, I'd have to create at least two renders of the same scene featuring the character. When there's more than one pregnancy, the figure multiplies.
The fact that TFTUV doesn't have as strict a narrative structure as SL had does help a lot of course. But if I'm going to show the women in various pregnant stages, I'd have to deal with the resulting babies at some point as well. I mean, I'm sure I could explain everything away by having a kindergarten on the ship, but I'd also have to deal with the mothers and MC as the father bringing up those children. Not sure if daycare is a very titillating storyline.
However, there will be pregnancies in the game and I might not do them all at once, like in Sisterly Lust. I haven't worked out the specifics yet for each character, but the bulk will probably begin in the latter half of act two. That should give me enough time to show all the bellies in all their glory, before the pregnancies get too advanced to take the women out of action.