Not using any hack at the moment. I have Tom's default everyday outfits available on MTS. What I do is make sure the pregnant sims always have a nightie that has the pregmorph and just swtich to it via twojeffs blender. Since they don't walk around on lots with pj's and underwear the default maternity set takes care of that part. I don't know if Squinge's newer preg wear anything is fixed in that regard, it has been a long time since I've used it. I could give it another go as it seems the default maternity pj's and underwear might be difficult for me to do.

You are right about the Npc's Sunni made. Hopefully she might have something in mind for the maternity stuff as well :D