This usually doesn't happen until she's showing, but my personal favorite are the bizarre things she wants, like wanting to eat spaghetti at the park, or eat some bizarre combination of food, like mac and cheese and cookies.
Oh, and if you don't like the pregnancy clothes the game generates, you can specify the outfit your sim will where while she's pregnant before she starts to show. Just go to a dresser and set an outfit that's one of the pregnancy-approved outfits, like the sundress that can also be a nightgown, or the sweatpants and the long sleeved tee with the short sleeved tee on top of it. Then you can edit the colors and patterns to your liking. I also recommend changing the shoes your sim wears with the outfit, especially if she normally wears high heels. There's just something not right about a pregnant sim waddling along while wearing high heels and sweatpants! Just make sure that once you set the outfit that it's what your sim is wearing when she begins to show, so I'd recommend wearing as soon as the first wave of nausea kicks in, just to be on the safe side.