Hi there. I think you are generally able to do whatever work outs you did before pregnancy or in early pregnancy with modification. My doctor put no restrictions on me at all with regards to exercise until I had an issue from falling down stairs (unrelated to working out, :>)).
Here's an article that might help with suggestions :
http://www.medhelp.org/pregnancy-health/articles/How-to-Exercise-Safely-When-Youre-Pregnant/2219
You should not lift more than twenty pounds while pregnant. They are correct when they say not to if you didn't before you were pregnant. It can cause stress on your baby if you push yourself. I swam for exercise with my first rather than lifting weights like I was. Walking, jogging and swimming are the best forms of exercise for an expecting mommy. I am starting to swim again and I feel great. Just remember, if you feel tired, rest. If you feel faint, sit down. Drink plenty of water and always remember to wear sunscreen on walks or jogs, especially wear it if you plan on swimming outdoors. Your more sensitive to uv rays while pregnant.
If you were exercising before pregnancy then it's okay but you might not be able to do the same amount of whatever it was beforehand.
What kind of exercises? Were you into exercising pre pregnancy?