How intensely can I exercise during these 9 months?
If you're not having any complications, you can and should exercise every day for about 30 minutes, according to the American College of Obstetrics and Gynecology. You can exercise at a similar intensity to your prepregnancy level as long as you stay well-hydrated and avoid overheating. A good rule of thumb is to not increase intensity or duration beyond what you are used to doing so you don't overexert yourself. Stop immediately if you feel lightheaded or have contractions or bleeding. Using the "talk test" is an easy way to monitor your intensity while exercising.
Here's how it works: During the warm-up phase of your workout, you should be able to carry on a conversation with little or no effort. During the most challenging phase, conversing should require quite a bit of effort. While in the cool-down phase of your workout, you should again be able to carry on a conversation with minimal effort.