your biggest concern should be having the piercing migrate out of the skin from the excessive pressure.. leaving a real nasty scar, worse then how the piercing gets when it stretches after taking the bar out.
change the bar to a flexible tygon (also used during xrays).depending on your body, and how deep the piercing was originally done, you should be able to keep it throughout the pregnancy.
good luck!
(tried to post a link to a site that sells tygon body jewellery but couldn't because i dont have enough posts!.. just google it!)