First and foremost find a Dr. you trust/respect for there opinion/advice.
you won't be lifting competitively and you won't be lifting heavy enough to strain. I don't have experience training the 'big lifts,' while I was pg but I did continue training, just not in the same way.
Every woman is different but I was so fatigued and achy, that a lot of weight lifting became harder and harder to keep up with. Especially as your body changes/grows, etc.
I think squats are the best to keep with pregnancy..DLs, not sure..and once you get past 3 months or so flat bench pressing will be out.
Training with weights for me was just a form of maintaining what I had..I stuck to a lot of machines towards the end.