I did a few events while pregnant, and the only real adjustments I had to make were drinking more water and being careful not to get too warm. That seems to lead to fainting. And, of course the obvious, no grog. As for clothing, in the beginning I just wore my stays a little looser...towards the end, I opted for a men's waistcoat over my shift and petticoat. Not entirely PC, but necessary for me at the time. My little girl hasn't been to any overnight events yet, but I bet Callenish and Salty could give you some pointers there. They're the pros.