It's best po to consult your OB, although kung medyo conservative ang doctor nyo ay baka di kayo payagan. In general, you can do modified versions of the exercises you do pre-pregnancy. Modified in a way na bawasan ang intensity at yung position dapat na hindi maiipit si baby. And also, just listen to your body.
Personally, yung mga stretchings na ginagawa ko before, continuous lng throughout my pregnancy. Yung dating bike to work ko naging walk to work. No more push-ups for me not even modified dahil takot rin ako 😅 When I lift heavy things, I engage my legs and arns more than my core muscles.