Most people can remain very active throughout the pregnancy, with my daughter I started working out around 20 weeks or so and did zumba twice a week and walked miles daily and felt great.
I do 15 minutes of stair master and walk on the treadmill for 30 minutes every evening.
There are a lot of pregnancy apps you can download and they have different workouts for the trimester you are in so they are safe.
Id talk to your dr.
I walked for about an hour a day up until the past three weeks but had to slow down due to a hip problem. My good friend ran through her whole pregnancy... like 8 to 10 miles a day.