Well as far as the womb goes an internal one may as well be expanded, not like normal women don't blow up while pregnant except in rare cases, so I can totally see a waifu bot swapping out parts to accommodate the fetus.
This stuff is actually pretty easy to think about if you separate the parts thinking about them individually while keeping in mind the most notable factors which are miniaturization and quantity/quality of moving parts. For instance:
The Womb:>is everything small enough to fit into her torso?>if you expand the torso can it contain the fetus then?>if not are you going to use an umbilical or a fixed mount for the waifus external womb?>does the waifu still have the components to fug while pregnant>if the womb is internal is it at a set size or is it designed to expand?>is the external shell designed to expand
I got lots of this stuff in mind but it takes a while to properly type it out