It's ok to use the word "fetus". According to Wikipedia:
The word fetus originates from the Latin fetus meaning "offspring," "act of bearing young," or "is or was filled with young". Foetus is an English variation on this rather than a Latin or Greek word, but has been in use since at least 1594 according to the OED, which describes fetus as etymologically preferable but almost unknown in actual use.
Although the pro-abort/pro-death crowd tries to dehumanize babies when it uses "fetus" instead of "baby", they are actually unknowingly confirming a child's humanity by using that word.
Baby shower does sound cuter than offspring shower or young-one shower, anyway. :)
They don't try to dehumanize babies, they succeed in dehumanizing them. "Fetus" may be the "correct" term, but people don't go to the hospital to deliver their "fetus", they go there to deliver their new baby.