Wear wrap-around lead (0.5mm thickness will do).
Stay out of rooms using cement.
Your baby bump can (eventually) hold retractors.
Wear TED hose.
Pee before OR cases.
Tell people if you want to. It is your body, your life, and your prerogative.
Your co-residents will appreciate a heads-up and will hopefully work with you on a modified call schedule so you can do your call duty earlier in pregnancy and have a little time after birth before going back into the call pool.
But again, congrats! Being a mother is the greatest joy (and sometimes frustration) you will ever know.