The second trimester
In the second trimester, you may begin to feel like your old self again (with the exception of your growing baby bump, of course!). Your nausea and morning sickness may finally be fading, and you might notice that you have more energy.
Physical changes in the second trimester are likely to include backaches caused by your growing belly, enlarged breasts, nasal congestion, headaches, heartburn, and weight gain—especially if you spent most of your first trimester suffering from morning sickness.
As long as you feel up to it, continue your current level of physical activity. You may even feel energized enough to increase the length or number of your workout sessions. That is entirely safe, as long as you listen to your body and don't overdo it.