You can continue doing any exercise you were previously doing. However, you should not elevate your core body temperature. General guidelines to help avoid this are to limit your target heart rate to 120-140 bpm or to make sure you can have a full conversation when at your max speed. Drink plenty of fluids before, during, and after exercise. Eat enough calories to meet the needs of your pregnancy and exercise program.
Stop exercising immediately if you have pain, bleeding, dizziness, or shortness of breath.
If you do not already exercise, you may want to start walking, stretching or doing yoga. The NCH Wellness Center offers Mommy 2 Be Water Aerobics and Yoga classed that are great for pregnant moms.