Quoting Live-Laugh-Love:" Nobody is forcing you to go though so you arent really depending on or expecting anything...especially ... [snip!] ... if you throw it for yourself. Imo it is less tacky to throw your own shower than to expect someone to throw it for you."
Baby showers can be expensive so I don't see why a mother can't throw one herself, it's not like the people are going to bring gifts that are for HER they're for her baby, so she's pretty much throwing a celebration for her baby to be and asking that people bring that baby a gift if they would like to attend. I don't see how it would be tacky. =/